Remove deprecated Audio APIs

[jodal]

We should remove all deprecated audio APIs:

• Audio.emit_end_of_stream() method

[sticken88]

Should we just remove it or replace it with something else/similar?

[kingosticks]

This is really just a reminder to remove these. Anything marked as deprecated for removal in the next major version should already be handled in some other way (or no longer required at all) in the current version.

In the case of Audio.emit_end_of_stream() the changelog has the details:

Deprecated mopidy.audio.Audio.emit_end_of_stream(). Pass a None buffer to mopidy.audio.Audio.emit_data() to end the stream. This should only affect Mopidy-Spotify.