move sample app to separate repo

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

@@ -27,14 +27,13 @@ apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
     compileSdkVersion 29
-    ndkVersion '21.3.6528147'
 
     sourceSets {
         main.java.srcDirs += 'src/main/kotlin'
     }
+
     lintOptions {
         disable 'InvalidPackage'
-        checkReleaseBuilds false
     }
 
     defaultConfig {
@@ -44,7 +43,6 @@ android {
         targetSdkVersion 29
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
-        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
     }
 
     buildTypes {
@@ -62,10 +60,4 @@ flutter {
 
 dependencies {
     implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
-    testImplementation 'junit:junit:4.12'
-    androidTestImplementation 'androidx.test:runner:1.1.1'
-    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
-    implementation 'com.google.firebase:firebase-messaging:20.1.2'
 }
-
-apply plugin: 'com.google.gms.google-services'