Bump Container Registry to v3.21.0-gitlab

What does this MR do?

3.21.0 (2022-01-06)

Bug Fixes

• correct typo cloudfront updatefrenquency (dddf7aa)
• handle missing foreign layers gracefully (ddb578a)

Features

• handlers: add gitlab v1 API base route (6efb384)

Related issues

gitlab-org/container-registry#550 (closed)

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated