Fixes client having authority over rules popup cvars (#28655)

* Fixes client having authority over rules popup cvars

* Delete duplicate migration

* Pre-update

* Post-update

Content.Server/Administration/Managers/AdminManager.cs

@@ -240,7 +240,6 @@ namespace Content.Server.Administration.Managers
             _sawmill = _logManager.GetSawmill("admin");
 
             _netMgr.RegisterNetMessage<MsgUpdateAdminStatus>();
-            _netMgr.RegisterNetMessage<ShowRulesPopupMessage>();
 
             // Cache permissions for loaded console commands with the requisite attributes.
             foreach (var (cmdName, cmd) in _consoleHost.AvailableCommands)