Cleanup - Use RemoveAllChildren() over DisposeAllChildren() (#39848)

* Content - change the (should-be-obsolete) DisposeAllChildren into the more robust RemoveAllChildren.

* Remove duplicate calls.

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Co-authored-by: ElectroJr <leonsfriedrich@gmail.com>

Content.Client/ContextMenu/UI/ContextMenuUIController.cs

@@ -95,7 +95,7 @@ namespace Content.Client.ContextMenu.UI
         /// </summary>
         public void Close()
         {
-            RootMenu.MenuBody.DisposeAllChildren();
+            RootMenu.MenuBody.RemoveAllChildren();
             CancelOpen?.Cancel();
             CancelClose?.Cancel();
             OnContextClosed?.Invoke();