git-multimail: update to release 1.2.0

git-multimail: update to release 1.2.0

The changes are described in CHANGES.

Contributions-by: Matthieu Moy <redacted>
Contributions-by: Elijah Newren <redacted>
Contributions-by: Edward d'Auvergne <redacted>
Contributions-by: Vadim Zeitlin <redacted>
Contributions-by: Paul Sokolovsky <redacted>
Contributions-by: Michael Haggerty <redacted>
Contributions-by: Elijah Newren <redacted>
Contributions-by: Richard Hansen <redacted>
Contributions-by: Job Snijders <redacted>
Signed-off-by: Matthieu Moy <redacted>
Signed-off-by: Junio C Hamano <redacted>