Fix FTBFS by installing b43-fwcutter from bullseye instead of sid

The b43-fwcutter in sid depends on libc6 >= 2.34 and we only have 2.31.
Using the version from bullseye instead should be no problem because
they are only one minor version apart (1:019-7 vs 1:019-8) and
according to the changelog the only changes are in debian/copyright and
translations.

Closes #19456