Remove --replaygain flag when checking bs1770gain availability
Remove --replaygain flag when checking bs1770gain availability

bs1770gain exits with error 1 when called without data, interpreted as unavailable

ibmibmibm/beets,beetbox/beets,jackwilsdon/beets,shamangeorge/beets,ibmibmibm/beets,shamangeorge/beets,sampsyo/beets,sampsyo/beets,ibmibmibm/beets,shamangeorge/beets,shamangeorge/beets,jackwilsdon/beets,sampsyo/beets,ibmibmibm/beets,beetbox/beets,beetbox/beets,jackwilsdon/beets,beetbox/beets,jackwilsdon/beets,sampsyo/beets