Fix: Avoid path in the template import (facebook#35394)

Summary:
Investigating [this comment](reactwg/react-native-releases#41 (comment)), I made some tests.
It seems like we can simply use `#import <RCTAppDelegate.h>` instead of the `#import <React-RCTAppDelegate/RCTAppDelegate.h>` in both setups:
- default setup
- `use_frameworks! :linkage => :static`

## Changelog

[iOS] [Fixed] - Support `use_framework! :linkage => :static` in template

Pull Request resolved: facebook#35394

Test Plan:
1. Manually tested with a new app
2. CircleCI
3. Sandcastle

Reviewed By: cortinico

Differential Revision: D41402060

Pulled By: cipolleschi

fbshipit-source-id: e1ed8196ed860b3663a88f5283f2745e39b0e944

template/ios/HelloWorld/AppDelegate.h

@@ -1,4 +1,4 @@
-#import <React-RCTAppDelegate/RCTAppDelegate.h>
+#import <RCTAppDelegate.h>
 #import <UIKit/UIKit.h>
 
 @interface AppDelegate : RCTAppDelegate