Merge pull request #4772 from dabit3/native-modules-docs-fix

fixed documentation error for native modules docs page

docs/NativeModulesIOS.md

@@ -374,7 +374,7 @@ Then create a private implementation file that will register the required inform
 
 @interface RCT_EXTERN_MODULE(CalendarManager, NSObject)
 
-RCT_EXTERN_METHOD(addEvent:(NSString *)name location:(NSString *)location date:(NSNumber *)date)
+RCT_EXTERN_METHOD(addEvent:(NSString *)name location:(NSString *)location date:(nonnull NSNumber *)date)
 
 @end
 ```