l10n: git.pot: v2.21.0 round 1 (214 new, 38 removed)

Generate po/git.pot from v2.21.0-rc0-30-g11ad41d4 (Seventh batch for 2.21)
for git v2.21.0 l10n round 1.
Signed-off-by: NJiang Xin <worldhello.net@gmail.com>