remove old wc.change_metadata test
remove old wc.change_metadata test

simon-weber/gmusicapi,peetahzee/Unofficial-Google-Music-API,simon-weber/Unofficial-Google-Music-API,TheOpenDevProject/gmusicapi,dvirtz/gmusicapi,thebigmunch/gmusicapi,dvirtz/gmusicapi,tanhaiwang/gmusicapi