Remove Banshee's sound menu support
I found out how to do it. In the extensions just only uncheck "Show Banshee in sound Menu" and that takes it off the sound menu.
I quote RSparker on Ubuntu Forums:
For the record, the entries of each individual player on the sound menu are stored in
~/.cache/indicators/sound/familiar-players-db.keyfileYou can either delete it and all the entries will be gone or selectively edit each entry.