Remove 6 empty Objective-C stub headers (#56949)

Summary:
Pull Request resolved: #56949

No behavior change — these headers contributed no symbols and the test exercised a deleted class.

Changelog:
[iOS][Removed] - Removed six empty Objective-C stub headers (`RCTJSIExecutorRuntimeInstaller.h`, `RCTRootContentView.h`, `RCTRootViewInternal.h`, `RCTNativeModule.h`, `RCTModalManager.h`, `RCTTextAttributes.h`) and the dead `RCTTextAttributesTest`.

Differential Revision: D106162524

Author: christophpurrer

packages/react-native/Libraries/AppDelegate/RCTAppSetupUtils.mm

@@ -7,7 +7,6 @@
 
 #import "RCTAppSetupUtils.h"
 
-#import <React/RCTJSIExecutorRuntimeInstaller.h>
 #import <react/renderer/runtimescheduler/RuntimeScheduler.h>
 #import <react/renderer/runtimescheduler/RuntimeSchedulerBinding.h>
 

packages/react-native/Libraries/Text/RCTTextAttributes.h

@@ -11,7 +11,6 @@
 #import <React/UIView+React.h>
 
 #import <React/RCTBackedTextInputDelegateAdapter.h>
-#import <React/RCTTextAttributes.h>
 
 @implementation RCTUITextView {
   UILabel *_placeholderView;

packages/react-native/Libraries/Text/TextInput/Multiline/RCTUITextView.mm

@@ -8,7 +8,6 @@
 #import <UIKit/UIKit.h>
 
 @protocol RCTBackedTextInputDelegate;
-@class RCTTextAttributes;
 
 NS_ASSUME_NONNULL_BEGIN
 

packages/react-native/Libraries/Text/TextInput/RCTBackedTextInputViewProtocol.h

@@ -8,7 +8,6 @@
 #import <React/RCTUITextField.h>
 
 #import <React/RCTBackedTextInputDelegateAdapter.h>
-#import <React/RCTTextAttributes.h>
 #import <React/RCTUtils.h>
 #import <React/UIView+React.h>
 

packages/react-native/Libraries/Text/TextInput/Singleline/RCTUITextField.mm

@@ -7,7 +7,6 @@
 
 #import "RCTRootView.h"
 #import "RCTRootViewDelegate.h"
-#import "RCTRootViewInternal.h"
 
 #import <objc/runtime.h>
 
@@ -19,7 +18,6 @@
 #import "RCTLog.h"
 #import "RCTPerformanceLogger.h"
 #import "RCTProfile.h"
-#import "RCTRootContentView.h"
 #import "RCTRootShadowView.h"
 #import "RCTTouchHandler.h"
 #import "RCTUIManager.h"

packages/react-native/React/Base/RCTRootContentView.h

@@ -15,7 +15,6 @@
 #import "RCTLog.h"
 #import "RCTPerformanceLogger.h"
 #import "RCTProfile.h"
-#import "RCTRootContentView.h"
 #import "RCTRootViewDelegate.h"
 #import "RCTSurface.h"
 #import "UIView+React.h"