Remove usage of UIApplication.sharedApplication (#34787)

Summary:
Brings in line with rest of code base and avoids running into this error
```
‘sharedApplication’ is unavailable: not available on iOS (App Extension) — Use view controller based solutions where appropriate instead.
```
when `Requires Only App-Extension-Safe-API` is set to Yes.

## Changelog

[iOS] [Fixed] - Update usage of UIApplication.sharedApplication in RCTKeyCommands

Pull Request resolved: #34787

Test Plan: Setting `Requires Only App-Extension-Safe-API` to Yes before this change means the app will not compile, after the change it does.

Reviewed By: dmytrorykun

Differential Revision: D39812410

Pulled By: cipolleschi

fbshipit-source-id: 78d185ba20301b10609e4a387f000f0cfda55663

React/Base/RCTKeyCommands.m

@@ -128,7 +128,7 @@ - (void)handleKeyUIEventSwizzle:(UIEvent *)event
     isKeyDown = [event _isKeyDown];
   }
 
-  BOOL interactionEnabled = !UIApplication.sharedApplication.isIgnoringInteractionEvents;
+  BOOL interactionEnabled = !RCTSharedApplication().isIgnoringInteractionEvents;
   BOOL hasFirstResponder = NO;
   if (isKeyDown && modifiedInput.length > 0 && interactionEnabled) {
     UIResponder *firstResponder = nil;