repo: upgrade to 2.15

BUG=None
TEST=CQ passes

Change-Id: Ida672094c2e620c8c140df602c232ddea3df1114
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2903767
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Stephane Belmon <sbelmon@google.com>
2 files changed