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/UserInterface/Systems/Hands/Controls/HandsContainer.cs

@@ -1,4 +1,4 @@
-using System.Linq;
+using System.Linq;
 using Content.Client.UserInterface.Systems.Inventory.Controls;
 using Robust.Client.UserInterface.Controls;
 
@@ -74,7 +74,7 @@ public sealed class HandsContainer : ItemSlotUIContainer<HandButton>
     public void Clear()
     {
         ClearButtons();
-        _grid.DisposeAllChildren();
+        _grid.RemoveAllChildren();
     }
 
     public IEnumerable<HandButton> GetButtons()