Fix @see tag for WitherSkeleton

Pointed out by xGhOsTkiLLeRx in Bukkit#229

By: md_5 <git@md-5.net>

paper-api/src/main/java/org/bukkit/entity/EntityType.java

@@ -38,7 +38,7 @@ public enum EntityType {
      */
     ELDER_GUARDIAN("elder_guardian", ElderGuardian.class, 4),
     /**
-     * @see WitherSkull
+     * @see WitherSkeleton
      */
     WITHER_SKELETON("wither_skeleton", WitherSkeleton.class, 5),
     /**