Use gitlab-base for certificates container

What does this MR do?

Use gitlab-base for certificates container

- Use gitlab-base instead of alpine as the base for the container filled
  with common public certificate authorities and a way to add others.

Closes https://gitlab.com/gitlab-org/charts/gitlab/-/issues/3446

Changelog: changed

Signed-off-by: Robert Marshall <rmarshall@gitlab.com>

Related issues

Closes gitlab-org/charts/gitlab#3446 (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