Fix package declarations for add-to-app integration tests (#77648)

dev/integration_tests/android_module_host_with_custom_build_v2_embedding/app/src/main/java/io/flutter/addtoapp/MainActivity.java

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-package io.flutter.add2app;
+package io.flutter.addtoapp;
 
 import io.flutter.embedding.android.FlutterActivity;
 

dev/integration_tests/module_host_with_custom_build_v2_embedding/app/src/main/java/io/flutter/addtoapp/MainActivity.java

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-package io.flutter.add2app;
+package io.flutter.addtoapp;
 
 import io.flutter.embedding.android.FlutterActivity;