remove push key when logout

lib/data/repository/authentication_repository.dart

@@ -42,6 +42,7 @@ class AuthenticationRepository {
 
   void logOut() {
     pref.saveString(DATA_CONST.TOKEN_KEY, "");
+    pref.saveString(DATA_CONST.PUSH_KEY, "");
     _controller.add(AuthenticationStatus.unauthenticated);
   }