Added newline at end of `.gitignore` files (#141270)

Added missing required newline at end of some `.gitignore` files. All other `.gitignore` files ends with a newline except the changed ones, hence the PR.

> *List which issues are fixed by this PR. You must list at least one issue. An issue is not required if the PR fixes something trivial like a typo.*

**Not listing any issues because of trivial fixes as mentioned above.**

AUTHORS

@@ -120,3 +120,4 @@ Sabin Neupane <sabin.neupane26@gmail.com>
 Mahdi Bagheri <1839491@gmail.com>
 Mok Kah Wai <taboosun1996@gmail.com>
 Lucas Saudon <lsaudon@gmail.com>
+Om Phatak <everythingoutdated@gmail.com>

dev/benchmarks/multiple_flutters/android/app/.gitignore

-/build
\ No newline at end of file
+/build

dev/integration_tests/android_embedding_v2_smoke_test/android/.gitignore

@@ -3,4 +3,4 @@ gradle-wrapper.jar
 /captures/
 /gradlew
 /gradlew.bat
-/local.properties
\ No newline at end of file
+/local.properties

dev/integration_tests/ios_add2app_life_cycle/.gitignore

@@ -66,4 +66,4 @@ fastlane/test_output
 # After new code Injection tools there's a generated folder /iOSInjectionProject
 # https://github.com/johnno1962/injectionforxcode
 
-iOSInjectionProject/
\ No newline at end of file
+iOSInjectionProject/

packages/flutter_tools/templates/plugin/ios.tmpl/.gitignore

@@ -35,4 +35,4 @@ Icon?
 
 /Flutter/Generated.xcconfig
 /Flutter/ephemeral/
-/Flutter/flutter_export_environment.sh
\ No newline at end of file
+/Flutter/flutter_export_environment.sh

packages/integration_test/ios/.gitignore

@@ -35,4 +35,4 @@ Icon?
 
 /Flutter/Generated.xcconfig
 /Flutter/ephemeral
-/Flutter/flutter_export_environment.sh
\ No newline at end of file
+/Flutter/flutter_export_environment.sh