[Bleeding] Cleanup clone methods.

By: Wesley Wolfe <weswolf@aol.com>

paper-api/src/main/java/org/bukkit/material/Stairs.java

@@ -92,4 +92,9 @@ public class Stairs extends MaterialData implements Directional {
     public String toString() {
         return super.toString() + " facing " + getFacing();
     }
+
+    @Override
+    public Stairs clone() {
+        return (Stairs) super.clone();
+    }
 }