Rename `Stop{SampleAndRemoveFilters -> }()`

Now that just one method for stopping samples is left, let's just
repurpose st as the general "stop global effects" method rather than
have it there with a hyperspecific name. It also has good symmetry, as
there already was a `Start()` method in the class.

osu.Game/Screens/Play/FailAnimation.cs

@@ -154,7 +154,10 @@ public void Start()
             Background?.FadeColour(OsuColour.Gray(0.3f), 60);
         }
 
-        public void StopSampleAndRemoveFilters()
+        /// <summary>
+        /// Stops any and all persistent effects added by the ongoing fail animation.
+        /// </summary>
+        public void Stop()
         {
             failSampleChannel?.Stop();
             removeFilters();

osu.Game/Screens/Play/Player.cs

@@ -1072,7 +1072,7 @@ public override void OnSuspending(ScreenTransitionEvent e)
         public override bool OnExiting(ScreenExitEvent e)
         {
             screenSuspension?.RemoveAndDisposeImmediately();
-            failAnimationLayer?.StopSampleAndRemoveFilters();
+            failAnimationLayer?.Stop();
 
             if (LoadedBeatmapSuccessfully)
             {