Fix styling for Admin Menu lists (#38261)

* remove styleclass from playertab 'button' lines

* cvar, fix button-style header alignment

* Fix requested changes

And also the extra cvar things I was meant to remove in the upstream merge

* Tiny tweaks

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Co-authored-by: Errant <35878406+Errant-4@users.noreply.github.com>

Content.Client/Administration/UI/Tabs/PlayerTab/PlayerTab.xaml.cs

@@ -172,6 +172,7 @@ public sealed partial class PlayerTab : Control
             _playerTabSymbolSetting);
         button.AddChild(entry);
         button.ToolTip = $"{player.Username}, {player.CharacterName}, {player.IdentityName}, {player.StartingJob}";
+        button.StyleClasses.Clear();
     }
 
     /// <summary>