repo: bump launcher version to 2.0

This reflects the transition to the new 2.x series which will be
migrating to Python 3-only.

Bug: https://crbug.com/gerrit/10418
Change-Id: I6355ac955d26b930f8a3721d3526eec5bed92400
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/253132


Reviewed-by: David Pursehouse <dpursehouse@collab.net>
Tested-by: Mike Frysinger <vapier@google.com>