fixed documentation error for native modules docs page

dabit3 · dabit3 · commit e2b035acf2dc · 2015-12-14T15:10:46.000-06:00
diff --git a/docs/NativeModulesIOS.md b/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
 ```
