docs: Remove UPnP-Inspector
docs: Remove UPnP-Inspector

Both UPnP-Inspector and its dependency Coherence seems unmaintained
since ~2009 and are not trivial to get running today.

kingosticks/mopidy,adamcik/mopidy,adamcik/mopidy,mopidy/mopidy,jodal/mopidy,jodal/mopidy,adamcik/mopidy,jcass77/mopidy,jodal/mopidy,kingosticks/mopidy,mopidy/mopidy,kingosticks/mopidy,mopidy/mopidy,jcass77/mopidy,jcass77/mopidy