Delete FlutterAppDelegate_Internal.h (#16772)

Author: cbracken

ci/licenses_golden/licenses_flutter

@@ -818,7 +818,6 @@ FILE: ../../../flutter/shell/platform/darwin/ios/framework/Headers/FlutterPlugin
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Headers/FlutterViewController.h
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Info.plist
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterAppDelegate.mm
-FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterAppDelegate_Internal.h
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterBinaryMessengerRelay.h
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterBinaryMessengerRelay.mm
 FILE: ../../../flutter/shell/platform/darwin/ios/framework/Source/FlutterBinaryMessengerRelayTest.mm

shell/platform/darwin/ios/BUILD.gn

@@ -46,7 +46,6 @@ shared_library("create_flutter_framework_dylib") {
 
   sources = [
     "framework/Source/FlutterAppDelegate.mm",
-    "framework/Source/FlutterAppDelegate_Internal.h",
     "framework/Source/FlutterBinaryMessengerRelay.mm",
     "framework/Source/FlutterCallbackCache.mm",
     "framework/Source/FlutterCallbackCache_Internal.h",