Fix CS0234: use global:: qualifier for Android.Graphics.Format in OsuGameActivity

Agent-Logs-Url: https://github.com/winnerspiros/osu/sessions/a24b8feb-25ae-4d67-afd0-495430d3e5c3

Co-authored-by: winnerspiros <1675249+winnerspiros@users.noreply.github.com>

Author: Copilot

osu.Android/OsuGameActivity.cs

@@ -267,7 +267,7 @@ protected override void OnCreate(Bundle? savedInstanceState)
                         // on the SurfaceHolder before SDL creates the VkAndroidSurfaceKHR.
                         try
                         {
-                            holder.SetFormat(Android.Graphics.Format.Rgba8888);
+                            holder.SetFormat(global::Android.Graphics.Format.Rgba8888);
                         }
                         catch (Exception e)
                         {