Refactor: Removes duplicated assets for `ItemMouth2` and `ItemMouth3`

Created by: elliesec

Summary

This is a follow-up to #2388, and uses DynamicGroupName to remove all assets in the ItemMouth2 and ItemMouth3 groups which were duplicating assets in ItemMouth. It also adds a missing Audio entry for the rope gag in ItemMouth3 that I noticed whilst testing.

I've manually tested all affected items to ensure that they all behave exactly as they did before.