fix test compatibility with mutagen 1.21
fix test compatibility with mutagen 1.21

The new Mutagen release got a fix for the bitrate calculation in Musepack. The
tests now reflect that.

moodboom/beets,shamangeorge/beets,m-urban/beets,jackwilsdon/beets,ttsda/beets,tima/beets,moodboom/beets,marcuskrahl/beets,mathstuf/beets,mried/beets,Wen777/beets,ttsda/beets,dfc/beets,lightwang1/beets,Andypsamp/CODjunit,shanemikel/beets,ruippeixotog/beets,beetbox/beets,beetbox/beets,Andypsamp/CODjunit,shamangeorge/beets,Freso/beets,ibmibmibm/beets,jbaiter/beets,randybias/beets,lightwang1/beets,jmwatte/beets,xsteadfastx/beets,bj-yinyan/beets,diego-plan9/beets,MyTunesFreeMusic/privacy-policy,shamangeorge/beets,lengtche/beets,pkess/beets,pkess/beets,kelvinhammond/beets,lightwang1/beets,mried/beets,swt30/beets,LordSputnik/beets,jayme-github/beets,pdf/beets,shanemikel/beets,Wen777/beets,YetAnotherNerd/beets,jmwatte/beets,bj-yinyan/beets,Kraymer/beets,untitaker/beets,sampsyo/beets,Freso/beets,Andypsamp/CODfinalJUNIT,Dishwishy/beets,Kraymer/beets,randybias/beets,andremiller/beets,artemutin/beets,m-urban/beets,Wen777/beets,Andypsamp/CODfinalJUNIT,bj-yinyan/beets,MyTunesFreeMusic/privacy-policy,YetAnotherNerd/beets,randybias/beets,moodboom/beets,imsparsh/beets,jcoady9/beets,Andypsamp/CODjunit,LordSputnik/beets,shamangeorge/beets,diego-plan9/beets,mried/beets,Andypsamp/CODfinalJUNIT,diego-plan9/beets,ruippeixotog/beets,Kraymer/beets,multikatt/beets,multikatt/beets,jbaiter/beets,shanemikel/beets,ibmibmibm/beets,mried/beets,arabenjamin/beets,jmwatte/beets,Dishwishy/beets,artemutin/beets,kelvinhammond/beets,pkess/beets,swt30/beets,bj-yinyan/beets,m-urban/beets,lengtche/beets,mosesfistos1/beetbox,untitaker/beets,jackwilsdon/beets,arabenjamin/beets,marcuskrahl/beets,sadatay/beets,andremiller/beets,asteven/beets,tima/beets,ttsda/beets,swt30/beets,swt30/beets,pkess/beets,pdf/beets,dfc/beets,beetbox/beets,marcuskrahl/beets,dfc/beets,Andypsamp/CODfinalJUNIT,jcoady9/beets,untitaker/beets,marcuskrahl/beets,jcoady9/beets,tima/beets,arabenjamin/beets,lengtche/beets,artemutin/beets,ibmibmibm/beets,artemutin/beets,mathstuf/beets,jackwilsdon/beets,PierreRust/beets,beetbox/beets,shanemikel/beets,sampsyo/beets,gabrielaraujof/beets,ttsda/beets,sampsyo/beets,PierreRust/beets,tima/beets,kareemallen/beets,jayme-github/beets,LordSputnik/beets,Kraymer/beets,LordSputnik/beets,jcoady9/beets,asteven/beets,Dishwishy/beets,parapente/beets,drm00/beets,lengtche/beets,asteven/beets,lightwang1/beets,imsparsh/beets,drm00/beets,multikatt/beets,madmouser1/beets,kareemallen/beets,Andypsamp/CODfinalJUNIT,SusannaMaria/beets,YetAnotherNerd/beets,MyTunesFreeMusic/privacy-policy,jackwilsdon/beets,madmouser1/beets,madmouser1/beets,ruippeixotog/beets,ruippeixotog/beets,untitaker/beets,Freso/beets,multikatt/beets,SusannaMaria/beets,xsteadfastx/beets,PierreRust/beets,sadatay/beets,gabrielaraujof/beets,sadatay/beets,YetAnotherNerd/beets,kelvinhammond/beets,krig/beets,arabenjamin/beets,m-urban/beets,gabrielaraujof/beets,imsparsh/beets,diego-plan9/beets,kareemallen/beets,randybias/beets,kelvinhammond/beets,xsteadfastx/beets,PierreRust/beets,jmwatte/beets,madmouser1/beets,krig/beets,SusannaMaria/beets,drm00/beets,asteven/beets,Andypsamp/CODjunit,dfc/beets,moodboom/beets,mosesfistos1/beetbox,MyTunesFreeMusic/privacy-policy,SusannaMaria/beets,kareemallen/beets,krig/beets,sampsyo/beets,andremiller/beets,imsparsh/beets,drm00/beets,parapente/beets,mosesfistos1/beetbox,xsteadfastx/beets,ibmibmibm/beets,gabrielaraujof/beets,mosesfistos1/beetbox,mathstuf/beets,Freso/beets,Andypsamp/CODjunit,parapente/beets,sadatay/beets,Dishwishy/beets,parapente/beets,mathstuf/beets