Fix server crash on shutdown due to DB notifications (#31379)

Fixes #31365

Content.Server/Database/ServerDbPostgres.Notifications.cs

@@ -97,6 +97,8 @@ public sealed partial class ServerDbPostgres
                 _notifyLog.Error($"Error in notification listener: {e}");
             }
         }
+
+        _notificationConnection.Dispose();
     }
 
     private void OnNotification(object _, NpgsqlNotificationEventArgs notification)
@@ -116,6 +118,5 @@ public sealed partial class ServerDbPostgres
             return;
 
         _notificationConnection.Notification -= OnNotification;
-        _notificationConnection.Dispose();
     }
 }