Remove broken image in README (#11170)

Github makes copies of images referenced in README, and it fails for large image sizes. The gif has 6MB and so is over the threshold.

This removes the image until I can figure out how to reinsert it so that it shows.

README.md

@@ -18,8 +18,6 @@ without losing state, on
 emulators, simulators, and hardware for iOS
 and Android.
 
-<img src="https://flutter.io/images/intellij/hot-reload.gif" alt="Make a change in your code, and your app is changed instantly.">
-
 ## Expressive, beautiful UIs
 
 Delight your users with Flutter's built-in