Additional steps to edit MainApplicaiton .java
Additional steps to edit MainApplicaiton .java

I was having build problems and was not able to use the underlying `FIRMessaging` object until I made this change.
riyaz942/react-native-fcm,evollu/react-native-fcm,riyaz942/react-native-fcm,riyaz942/react-native-fcm,evollu/react-native-fcm,evollu/react-native-fcm