Add Override annotations where appropriate

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

paper-server/src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -1847,6 +1847,7 @@ public final class CraftServer implements Server {
         }
     }
 
+    @Override
     public LootTable getLootTable(NamespacedKey key) {
         Validate.notNull(key, "NamespacedKey cannot be null");