Converts AdminMenu to partially use XAML (#3231)

Content.Client/UserInterface/AdminMenu/Tabs/AtmosTab/AtmosTab.xaml.cs

@@ -0,0 +1,11 @@
+#nullable enable
+using Robust.Client.AutoGenerated;
+using Robust.Client.UserInterface.Controls;
+
+namespace Content.Client.UserInterface.AdminMenu.Tabs.AtmosTab
+{
+    [GenerateTypedNameReferences]
+    public partial class AtmosTab : MarginContainer
+    {
+    }
+}