Remove no longer required nested object reposition hacks

As touched on in
ppy#30237 (comment), these
types of maneouvers are no longer required after
ppy#30021 - although as it turns out on
closer inspection, these things being there still *did not actually
break anything*, because the `slider.Path` mutation at the end of
`modifySlider()` causes `updateNestedPositions()` to be called
eventually anyway. So this is at mostly a code quality upgrade.

osu.Game.Rulesets.Osu/Utils/OsuHitObjectGenerationUtils.cs

@@ -3,7 +3,6 @@
 
 using System;
 using System.Linq;
-using osu.Framework.Extensions.IEnumerableExtensions;
 using osu.Game.Rulesets.Osu.UI;
 using osu.Game.Rulesets.Objects;
 using osu.Game.Rulesets.Osu.Beatmaps;
@@ -117,10 +116,9 @@ public static void ReflectHorizontallyAlongPlayfield(OsuHitObject osuObject)
             if (osuObject is not Slider slider)
                 return;
 
-            void reflectNestedObject(OsuHitObject nested) => nested.Position = new Vector2(OsuPlayfield.BASE_SIZE.X - nested.Position.X, nested.Position.Y);
             static void reflectControlPoint(PathControlPoint point) => point.Position = new Vector2(-point.Position.X, point.Position.Y);
 
-            modifySlider(slider, reflectNestedObject, reflectControlPoint);
+            modifySlider(slider, reflectControlPoint);
         }
 
         /// <summary>
@@ -134,10 +132,9 @@ public static void ReflectVerticallyAlongPlayfield(OsuHitObject osuObject)
             if (osuObject is not Slider slider)
                 return;
 
-            void reflectNestedObject(OsuHitObject nested) => nested.Position = new Vector2(nested.Position.X, OsuPlayfield.BASE_SIZE.Y - nested.Position.Y);
             static void reflectControlPoint(PathControlPoint point) => point.Position = new Vector2(point.Position.X, -point.Position.Y);
 
-            modifySlider(slider, reflectNestedObject, reflectControlPoint);
+            modifySlider(slider, reflectControlPoint);
         }
 
         /// <summary>
@@ -146,10 +143,9 @@ public static void ReflectVerticallyAlongPlayfield(OsuHitObject osuObject)
         /// <param name="slider">The slider to be flipped.</param>
         public static void FlipSliderInPlaceHorizontally(Slider slider)
         {
-            void flipNestedObject(OsuHitObject nested) => nested.Position = new Vector2(slider.X - (nested.X - slider.X), nested.Y);
             static void flipControlPoint(PathControlPoint point) => point.Position = new Vector2(-point.Position.X, point.Position.Y);
 
-            modifySlider(slider, flipNestedObject, flipControlPoint);
+            modifySlider(slider, flipControlPoint);
         }
 
         /// <summary>
@@ -159,18 +155,13 @@ public static void FlipSliderInPlaceHorizontally(Slider slider)
         /// <param name="rotation">The angle, measured in radians, to rotate the slider by.</param>
         public static void RotateSlider(Slider slider, float rotation)
         {
-            void rotateNestedObject(OsuHitObject nested) => nested.Position = rotateVector(nested.Position - slider.Position, rotation) + slider.Position;
             void rotateControlPoint(PathControlPoint point) => point.Position = rotateVector(point.Position, rotation);
 
-            modifySlider(slider, rotateNestedObject, rotateControlPoint);
+            modifySlider(slider, rotateControlPoint);
         }
 
-        private static void modifySlider(Slider slider, Action<OsuHitObject> modifyNestedObject, Action<PathControlPoint> modifyControlPoint)
+        private static void modifySlider(Slider slider, Action<PathControlPoint> modifyControlPoint)
         {
-            // No need to update the head and tail circles, since slider handles that when the new slider path is set
-            slider.NestedHitObjects.OfType<SliderTick>().ForEach(modifyNestedObject);
-            slider.NestedHitObjects.OfType<SliderRepeat>().ForEach(modifyNestedObject);
-
             var controlPoints = slider.Path.ControlPoints.Select(p => new PathControlPoint(p.Position, p.Type)).ToArray();
             foreach (var point in controlPoints)
                 modifyControlPoint(point);