Clean up apt list in a few containers

What does this MR do?

This saves about 18 MB in a number of images:

Image	Before	After
registry.gitlab.com/gitlab-org/build/cng/gitlab-ruby	382 MB	364 MB
registry.gitlab.com/gitlab-org/build/cng/gitlab-mailroom	648 MB	630 MB
registry.gitlab.com/gitlab-org/build/cng/gitaly	967 MB	949 MB
registry.gitlab.com/gitlab-org/build/cng/gitlab-webservice-ee	1.79 GB	1.77 GB

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