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/Access/UI/AccessOverriderWindow.xaml.cs

@@ -25,7 +25,7 @@ namespace Content.Client.Access.UI
         public void SetAccessLevels(IPrototypeManager protoManager, List<ProtoId<AccessLevelPrototype>> accessLevels)
         {
             _accessButtons.Clear();
-            AccessLevelGrid.DisposeAllChildren();
+            AccessLevelGrid.RemoveAllChildren();
 
             foreach (var access in accessLevels)
             {