[Docs] Remove outdated Objective-C launch screen setup instructions

[joshkeldam]

Description

As an engineer setting up a new React Native project, trying to configure the launch screen, when I follow the documentation, I find Objective-C code that references methods that don't exist in the modern Swift AppDelegate. It would be better if this outdated code was removed or clearly marked as legacy-only.

The documentation includes this Objective-C snippet:

// Place this code after "[self.window makeKeyAndVisible]" and before "return YES;"
UIStoryboard *sb = [UIStoryboard storyboardWithName:@"LaunchScreen" bundle:nil];
UIViewController *vc = [sb instantiateInitialViewController];
rootView.loadingView = vc.view;

This is confusing because:

• New React Native projects (0.71+) generate AppDelegate.swift by default
• The Swift AppDelegate doesn't have [self.window makeKeyAndVisible] or similar methods
• The launch screen already works automatically via LaunchScreen.storyboard without any code
• Developers waste time trying to convert this to Swift or figure out where to place it

Documentation version

0.71+ (latest), next

Documentation Location