repo-updater: Migrate AWS CodeCommit to new syncer
Created by: mrnugget
This fixes https://github.com/sourcegraph/sourcegraph/issues/3465 by migrating the AWS CodeCommit external services to the new syncer.
TODOs:
-
Add Changelog
Test plan: go test
+ manual testing (setup AWS CC on master
with enabled/disabled repos, then switch to this branch, boot up repo-updater)