Fixed path in change playlist details

The correct path for the "Change Playlist Details" request is:
https://api.spotify.com/v1/users/{user_id}/playlists/{playlist_id}

As shown under "Endpoint" in the web api documentation here:
https://developer.spotify.com/web-api/change-playlist-details/

However, the path in the module had "/tracks" appended to the end of the correct path.