Update 'Check if current user follows playlist' documentation and not use ids parameter

[Landcross]

Currently, the implementation for this endpoint seems to be out of date in Spotipy. Two things:

• It uses the ids query parameter that is marked as deprecated in the Spotify documentation
• Besides the fact that it is deprecated, Spotify documentation states that if you do you use, it can contain a maximum of 1 ID (1 user). The Spotipy documentation (in the code) however, states a maximum of 5 ids (users)

[dieser-niko]

Hi there, sorry for the late reply, but we've both been rather busy recently.

I've noticed that there are a bunch of outdated endpoints in our library, we are probably going to create a PR to update all of them.