Fix missing AppDelegate 4.2 migration

Method was renamed and when launching the tests the test host failed
due to this

Test Host/AppDelegate.swift

@@ -14,7 +14,7 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
     var window: UIWindow?
 
 
-    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
+    private func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
         // Override point for customization after application launch.
         return true
     }