audio/musicpc: update to 0.34

ChangeLog: https://raw.githubusercontent.com/MusicPlayerDaemon/mpc/v0.34/NEWS

 * add commands "albumart", "readpicture"
 * don't print status after error
 * custom status format
 * support grouping "list" results
 * meson: auto-build libmpdclient if not available
 * require libmpdclient 2.16 or newer
 * require MPD 0.21 or newer

PR:	263938
Reported by:	uzsolt@uzsolt.hu (maintainer)