Drop process scrape-config

What does this MR do?

In !4853 (merged) we removed support for process metrics coming from gitlab-exporter. However, we did not remove it as a scrape target for Prometheus, which now results in 404s being returned to the scraper since the /process endpoint does not exist anymore.

Related issues

• gitlab#290765 (closed)

Test plan

1. Pull a broken image, e.g. gitlab-ee:13.7.3-rfbranch.240047598.5b97c993-0
2. Make sure that prometheus is running and go to localhost:9090/targets; you should see that the gitlab_exporter_process target is not UP and scraping fails with server returned HTTP status 404 Not Found
3. Stop broken image and pull image from this MR
4. Look at /targets again; there should be no gitlab_exporter_process anymore

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
• Pipeline is green on dev.gitlab.org if the change is touching anything besides documentation or internal cookbooks
• trigger-package has a green pipeline running against latest commit

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• [-] Documentation created/updated
• Tests added removed
• [-] Integration tests added to GitLab QA
• [-] Equivalent MR/issue for the GitLab Chart opened. Not necessary I believe, see !4912 (comment 483370843)