Merge pull request #21501 from peppy/fix-first-run-button-colours

Fix first run beatmap screen button colours looking incorrect with new triangle effect

osu.Game/Overlays/FirstRunSetup/ProgressRoundedButton.cs

@@ -81,7 +81,7 @@ public void Complete()
             loading.Hide();
             tick.FadeIn(500, Easing.OutQuint);
 
-            Background.FadeColour(colours.Green, 500, Easing.OutQuint);
+            this.TransformTo(nameof(BackgroundColour), colours.Green, 500, Easing.OutQuint);
             progressBar.FillColour = colours.Green;
 
             this.TransformBindableTo(progressBar.Current, 1, 500, Easing.OutQuint);