use collection expression instead of stackalloc

osu.Game/Utils/GeometryUtils.cs

@@ -325,13 +325,8 @@ namespace osu.Game.Utils
                 return d;
 
             // Otherwise, must be on the boundary of the MEC
-            // Stackalloc to avoid allocations. It's safe to assume that the length of r will be at most 3
-            Span<Vector2> r2 = stackalloc Vector2[r.Length + 1];
-            r.CopyTo(r2);
-            r2[r.Length] = p;
-
             // Return the MEC for P - {p} and R U {p}
-            return welzlHelper(points, r2, n - 1);
+            return welzlHelper(points, [..r, p], n - 1);
         }
 
         #endregion