fix(ui): sample app gradle fixes

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

@@ -26,7 +26,7 @@ apply plugin: 'kotlin-android'
 apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
 
 android {
-    compileSdkVersion 30
+    compileSdkVersion 31
 
     sourceSets {
         main.java.srcDirs += 'src/main/kotlin'
@@ -41,7 +41,7 @@ android {
         // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
         applicationId "com.example.example"
         minSdkVersion 21
-        targetSdkVersion 30
+        targetSdkVersion 31
         versionCode flutterVersionCode.toInteger()
         versionName flutterVersionName
     }

packages/stream_chat_flutter/example/android/app/src/main/AndroidManifest.xml

@@ -16,6 +16,7 @@
             android:theme="@style/LaunchTheme"
             android:configChanges="orientation|keyboardHidden|keyboard|screenSize|smallestScreenSize|locale|layoutDirection|fontScale|screenLayout|density|uiMode"
             android:hardwareAccelerated="true"
+            android:exported="true"
             android:windowSoftInputMode="adjustResize">
             <!-- Specifies an Android theme to apply to this Activity as soon as
                  the Android process has started. This theme is visible to the user

packages/stream_chat_flutter/example/android/build.gradle

@@ -1,5 +1,5 @@
 buildscript {
-    ext.kotlin_version = '1.5.20'
+    ext.kotlin_version = '1.6.0'
     repositories {
         google()
         jcenter()