Revert "Add a deprecation javadoc note to the old FlutterActivity (#15156)" (#15331)

This reverts commit 293cd971.

shell/platform/android/io/flutter/app/FlutterActivity.java

@@ -16,17 +16,12 @@ import io.flutter.plugin.common.PluginRegistry;
 import io.flutter.view.FlutterNativeView;
 import io.flutter.view.FlutterView;
 
-// This uses a javadoc deprecation instead of a deprecation annotation because we don't want to show
-// a build-time warning yet. Revise once v2 embedding usage volume increases.
 /**
  * Base class for activities that use Flutter.
- *
- * @deprecated As of Flutter v1.12, this class is deprecated in favor of {@link io.flutter.embedding.android.FlutterActivity}.
- *             See https://flutter.dev/go/android-project-migration for migration details.
  */
 public class FlutterActivity extends Activity implements FlutterView.Provider, PluginRegistry, ViewFactory {
     private static final String TAG = "FlutterActivity";
-
+    
     private final FlutterActivityDelegate delegate = new FlutterActivityDelegate(this, this);
 
     // These aliases ensure that the methods we forward to the delegate adhere