fix(messaging,ios): crash receiving notification with image (#3701)

Currently receiving notifications with images will crash the app on iOS (Fixes #3447, #3616).

Patch proposed by @actuosus, thanks to him 🙌 #3447 (comment)

[publish]

packages/messaging/ios/RNFBMessaging/RNFBMessagingSerializer.m

@@ -113,7 +113,7 @@ + (NSDictionary *)remoteMessageUserInfoToDict:(NSDictionary *)userInfo {
     }
 
     // message.mutableContent
-    if (apsDict[@"mutable-content"] != nil && [apsDict[@"mutable-content"] isEqualToString:@"1"]) {
+    if (apsDict[@"mutable-content"] != nil && [apsDict[@"mutable-content"] intValue] == 1) {
       message[@"mutableContent"] = @([RCTConvert BOOL:apsDict[@"mutable-content"]]);
     }