docs: Remove mention of grooveshark extension (cherry picked from commit 5df1d689c1751dae4601bc9c57e51f3dddc88f22)
docs: Remove mention of grooveshark extension
(cherry picked from commit 5df1d689c1751dae4601bc9c57e51f3dddc88f22)

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