Revert "PORT: Allows Markings to Set Custom Layers for Specific Sprites (#2516)"

This reverts commit 9f39c112ad.

Content.IntegrationTests/Tests/Sprite/ItemSpriteTest.cs

@@ -28,11 +28,7 @@ public sealed class PrototypeSaveTest
     {
         // The only prototypes that should get ignored are those that REQUIRE setup to get a sprite. At that point it is
         // the responsibility of the spawner to ensure that a valid sprite is set.
-        "VirtualItem",
-        "MobGoblin", // imp edits - these four prototypes are species and do not receive their sprite data from ItemComponent, causing a false positive
-        "MobGoblinStowaway",
-        "MobGoblinKnight",
-        "MobGoblinCastaway",
+        "VirtualItem"
     };
 
     [Test]