git: upgraded package to upstream

Upgraded dev-vcs/git to version 2.21.0 on amd64

BUG=chromium:991071
TEST=Built package for an overlay that has a CROS_WORKON_COMMIT

Change-Id: I5474926aa39ddcbadd9f4c38b02d9ab529a943e9
Reviewed-on: https://chromium-review.googlesource.com/1737170
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
8 files changed