Revert "core: Add TODO for testing unplayable-by-backend tracks"
Revert "core: Add TODO for testing unplayable-by-backend tracks"

This reverts commit 3a8d896146f6bc443b76f8d9689cb7510fc304e0.

vrs01/mopidy,jcass77/mopidy,vrs01/mopidy,kingosticks/mopidy,mopidy/mopidy,vrs01/mopidy,ZenithDK/mopidy,kingosticks/mopidy,jodal/mopidy,adamcik/mopidy,jcass77/mopidy,jodal/mopidy,jodal/mopidy,adamcik/mopidy,mopidy/mopidy,mopidy/mopidy,adamcik/mopidy,kingosticks/mopidy,jcass77/mopidy,ZenithDK/mopidy,vrs01/mopidy,ZenithDK/mopidy,ZenithDK/mopidy