Update issue templates (#17250)

The "about" text was apparently too long.

.github/ISSUE_TEMPLATE/ACTIVATION.md

----
-name: I am having difficulty installing Flutter or getting it to work
-about: You have run into problems while downloading or installing Flutter,
-  or the "flutter" tool is crashing, or you are running into some other
-  issue before even being able to use "flutter run".
-
----
-
-<!-- Thank you for using Flutter!
-
-     If you are looking for support, please check out our documentation
-     or consider asking a question on Stack Overflow:
-      * https://flutter.io/
-      * https://docs.flutter.io/
-      * https://stackoverflow.com/questions/tagged/flutter?sort=frequent
-
-     If you have found a bug or if our documentation doesn't have an answer
-     to what you're looking for, then fill our the template below. Please read
-     our guide to filing a bug first:  https://flutter.io/bug-reports/
--->
-
-## Steps to Reproduce
-
-<!-- Please tell us exactly how to reproduce the problem you are running into. -->
- 
-1. ...
-2. ...
-3. ...
-
-## Logs
-
-<!--
-      Include the full logs of the commands you are running between the lines
-      with the backticks below. If you are running any "flutter" commands,
-      please include the output of running them with "--verbose"; for example,
-      the output of running "flutter --verbose create foo".
--->
-
-```
-```
-
-<!-- If possible, paste the output of running `flutter doctor -v` here. -->
-
-```
-```
+---
+name: I am having difficulty installing Flutter or getting it to work
+about: You have run into problems while downloading or installing Flutter, or the
+  "flutter" tool is crashing, or you are running into some other issue before even
+  being able to use "flutter run".
+
+---
+
+<!-- Thank you for using Flutter!
+
+     If you are looking for support, please check out our documentation
+     or consider asking a question on Stack Overflow:
+      * https://flutter.io/
+      * https://docs.flutter.io/
+      * https://stackoverflow.com/questions/tagged/flutter?sort=frequent
+
+     If you have found a bug or if our documentation doesn't have an answer
+     to what you're looking for, then fill our the template below. Please read
+     our guide to filing a bug first:  https://flutter.io/bug-reports/
+-->
+
+## Steps to Reproduce
+
+<!-- Please tell us exactly how to reproduce the problem you are running into. -->
+ 
+1. ...
+2. ...
+3. ...
+
+## Logs
+
+<!--
+      Include the full logs of the commands you are running between the lines
+      with the backticks below. If you are running any "flutter" commands,
+      please include the output of running them with "--verbose"; for example,
+      the output of running "flutter --verbose create foo".
+-->
+
+```
+```
+
+<!-- If possible, paste the output of running `flutter doctor -v` here. -->
+
+```
+```

.github/ISSUE_TEMPLATE/BUG.md

----
-name: I have a problem with my Flutter application.
-about: You are writing an application with Flutter but a widget is rendering
-  incorrectly, the application is crashing, there's an exception in the logs,
-  a widget is behaving badly, or some other such problem is manifesting.
-
----
-
-<!-- Thank you for using Flutter!
-
-     If you are looking for support, please check out our documentation
-     or consider asking a question on Stack Overflow:
-      * https://flutter.io/
-      * https://docs.flutter.io/
-      * https://stackoverflow.com/questions/tagged/flutter?sort=frequent
-
-     If you have found a bug or if our documentation doesn't have an answer
-     to what you're looking for, then fill our the template below. Please read
-     our guide to filing a bug first:  https://flutter.io/bug-reports/
--->
-
-## Steps to Reproduce
-
-<!--
-     Please tell us exactly how to reproduce the problem you are running into.
-
-     Please attach a small application (ideally just one main.dart file) that
-     reproduces the problem. You could use https://gist.github.com/ for this.
-
-     If the problem is with your application's rendering, then please attach
-     a screenshot and explain what the problem is.
--->
- 
-1. ...
-2. ...
-3. ...
-
-## Logs
-
-<!--
-      Run your application with `flutter run --verbose` and attach all the
-      log output below between the lines with the backticks. If there is an
-      exception, please see if the error message includes enough information
-      to explain how to solve the issue.
--->
-
-```
-```
-
-<!--
-     Run `flutter analyze` and attach any output of that command below.
-     If there are any analysis errors, try resolving them before filing this issue.
--->
-
-```
-```
-
-<!-- Finally, paste the output of running `flutter doctor -v` here. -->
-
-```
-```
+---
+name: I have a problem with my Flutter application.
+about: You are writing an application with Flutter but the application is crashing
+  or throws an exception, a widget is buggy, or something looks wrong.
+
+---
+
+<!-- Thank you for using Flutter!
+
+     If you are looking for support, please check out our documentation
+     or consider asking a question on Stack Overflow:
+      * https://flutter.io/
+      * https://docs.flutter.io/
+      * https://stackoverflow.com/questions/tagged/flutter?sort=frequent
+
+     If you have found a bug or if our documentation doesn't have an answer
+     to what you're looking for, then fill our the template below. Please read
+     our guide to filing a bug first:  https://flutter.io/bug-reports/
+-->
+
+## Steps to Reproduce
+
+<!--
+     Please tell us exactly how to reproduce the problem you are running into.
+
+     Please attach a small application (ideally just one main.dart file) that
+     reproduces the problem. You could use https://gist.github.com/ for this.
+
+     If the problem is with your application's rendering, then please attach
+     a screenshot and explain what the problem is.
+-->
+ 
+1. ...
+2. ...
+3. ...
+
+## Logs
+
+<!--
+      Run your application with `flutter run --verbose` and attach all the
+      log output below between the lines with the backticks. If there is an
+      exception, please see if the error message includes enough information
+      to explain how to solve the issue.
+-->
+
+```
+```
+
+<!--
+     Run `flutter analyze` and attach any output of that command below.
+     If there are any analysis errors, try resolving them before filing this issue.
+-->
+
+```
+```
+
+<!-- Finally, paste the output of running `flutter doctor -v` here. -->
+
+```
+```