Fix mania hold note heads hiding when frozen

This was an insidious regression from a3dc1d5. Prior to that commit,
`DrawableHoldNoteHead` had `UpdateStateTransforms()` overridden, to set
the hold note head's lifetime. When that method was split into
`UpdateInitialStateTransforms()` and `UpdateHitStateTransforms()`, the
lifetime set was moved to the former.

Unfortunately, that override served two purposes: both to set the
lifetime, and to suppress hit animations which would normally be added
by the base `DrawableManiaHitObject`. That fact being missed led to
`UpdateHitStateTransforms()` hiding the hold note head immediately on
hit and with a slight delay on miss.

To resolve, explicitly override `UpdateHitStateTransforms()` and
suppress the base call, with an explanatory comment.

osu.Game.Rulesets.Mania/Objects/Drawables/DrawableHoldNoteHead.cs

@@ -1,6 +1,8 @@
 // Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
 // See the LICENCE file in the repository root for full licence text.
 
+using osu.Game.Rulesets.Objects.Drawables;
+
 namespace osu.Game.Rulesets.Mania.Objects.Drawables
 {
     /// <summary>
@@ -25,6 +27,14 @@ namespace osu.Game.Rulesets.Mania.Objects.Drawables
             LifetimeEnd = LifetimeStart + 30000;
         }
 
+        protected override void UpdateHitStateTransforms(ArmedState state)
+        {
+            // suppress the base call explicitly.
+            // the hold note head should never change its visual state on its own due to the "freezing" mechanic
+            // (when hit, it remains visible in place at the judgement line; when dropped, it will scroll past the line).
+            // it will be hidden along with its parenting hold note when required.
+        }
+
         public override bool OnPressed(ManiaAction action) => false; // Handled by the hold note
 
         public override void OnReleased(ManiaAction action)