LAKITU: libsync: Update project URL

The project has moved to chromium.googlesource.com. I'll upstream this
change once we land the ChromeOS upgrade in COS.

BUG=b/192265868
TEST=local BE run
RELEASE_NOTE=None

Change-Id: Ib3dc1da225a9f52922991c2e30e78c6e621882cc
Reviewed-on: https://cos-review.googlesource.com/c/third_party/overlays/chromiumos-overlay/+/19115
Tested-by: Robert Kolchmeyer <rkolchmeyer@google.com>
Reviewed-by: Vaibhav Rustagi <vaibhavrustagi@google.com>