Remove `[Virtual]` from some classes that shouldn't have it (#43347)

* Remove [Virtual] from some classes that shouldn't have it

* Back to virtual with you

Content.Client/Stylesheets/Stylesheets/NanotrasenStylesheet.Palettes.cs

@@ -2,7 +2,7 @@
 
 namespace Content.Client.Stylesheets.Stylesheets;
 
-public sealed partial class NanotrasenStylesheet
+public partial class NanotrasenStylesheet
 {
     public override ColorPalette PrimaryPalette => Palettes.Navy;
     public override ColorPalette SecondaryPalette => Palettes.Slate;

Content.Client/UserInterface/Controls/RadialMenu.cs

@@ -228,7 +228,6 @@ public class RadialMenu : BaseWindow
 /// Base class for radial menu buttons. Excludes all actions except clicks and alt-clicks
 /// from interactions.
 /// </summary>
-[Virtual]
 public abstract class RadialMenuButtonBase : BaseButton
 {
     /// <inheritdoc />

Content.Client/UserInterface/Controls/SlotControl.cs

@@ -9,7 +9,6 @@ using Robust.Shared.Prototypes;
 
 namespace Content.Client.UserInterface.Controls
 {
-    [Virtual]
     public abstract class SlotControl : Control, IEntityControl
     {
         public static int DefaultButtonSize = 64;

Content.Client/UserInterface/Systems/Inventory/Controls/ItemSlotUIContainer.cs

@@ -11,7 +11,6 @@ public interface IItemslotUIContainer
     public bool TryAddButton(SlotControl control);
 }
 
-[Virtual]
 public abstract class ItemSlotUIContainer<T> : GridContainer, IItemslotUIContainer where T : SlotControl
 {
     private readonly Dictionary<string, T> _buttons = new();