WireGuardApp: Fix window background color to default black

Signed-off-by: Andrej Mihajlov <and@mullvad.net>

Sources/WireGuardApp/UI/iOS/AppDelegate.swift

@@ -21,11 +21,6 @@ class AppDelegate: UIResponder, UIApplicationDelegate {
         }
 
         let window = UIWindow(frame: UIScreen.main.bounds)
-        if #available(iOS 13.0, *) {
-            window.backgroundColor = .systemBackground
-        } else {
-            window.backgroundColor = .white
-        }
         self.window = window
 
         let mainVC = MainViewController()