Add @generated tag int Fabric codegen files

Summary:
This diff adds the generated tog to codegen files

changelog: [internal] internal

Reviewed By: fkgozali

Differential Revision: D23117527

fbshipit-source-id: 600013425deeb08321761622e13e7cf9a0f0db38

packages/react-native-codegen/src/generators/modules/GenerateModuleCpp.js

@@ -48,6 +48,8 @@ const template = `
  *
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
+ *
+ * ${'@'}generated by codegen project: GenerateModuleH.js
  */
 
 #include <react/modules/::_LIBRARY_NAME_::/NativeModules.h>