chore(app-installations): move example app to "flutterfire-e2e-tests" Firebase project (#10044)

* chore(app-installations): move example app to "flutterfire-e2e-tests" Firebase project

* license header & rm file

* removed ext.kotlin from build.gradle

Author: russellwheatley

packages/firebase_app_installations/firebase_app_installations/example/android/app/build.gradle

@@ -27,7 +27,7 @@ apply plugin: 'com.google.gms.google-services'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion 30
+    compileSdkVersion 31
 
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_1_8