gitlab-rails: remove ee/spec/ if present

What does this MR do?

Remove ee/spec/ if present within /srv/gitlab. Save ~30MB in gitlab-rails, and thus all images built upon it.

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

Closes #2670