Fix rsi sprite access for verbs (#14284)

Content.Server/Humanoid/Systems/HumanoidSystem.Modifier.cs

@@ -4,6 +4,7 @@ using Content.Shared.Humanoid;
 using Content.Shared.Verbs;
 using Robust.Server.GameObjects;
 using Robust.Server.Player;
+using Robust.Shared.Utility;
 
 namespace Content.Server.Humanoid;
 
@@ -28,7 +29,7 @@ public sealed partial class HumanoidAppearanceSystem
         {
             Text = "Modify markings",
             Category = VerbCategory.Tricks,
-            IconTexture = "/Textures/Mobs/Customization/reptilian_parts.rsi/tail_smooth.png",
+            Icon = new SpriteSpecifier.Rsi(new ResourcePath("/Textures/Mobs/Customization/reptilian_parts.rsi"), "tail_smooth"),
             Act = () =>
             {
                 _uiSystem.TryOpen(uid, HumanoidMarkingModifierKey.Key, actor.PlayerSession);