Remove direct activesupport dependency

This merge request does not really remove activesupport dependency, because we're still depending on it through other dependencies

Remove direct activesupport dependency because we don't want to encourage using it. We still can't easily drop the indirect dependency because:

• gitlab-styles <- rubocop-rails <- activesupport
  • We can probably make this optional from gitlab-style. There's no Rails here
• gitlab-triage <- activesupport
  • This we can control
• gitlab-triage <- globalid <- activesupport
  • This is used minimally, which I think we can potentially drop
• gitlab-triage <- graphql-client <- activesupport
  • This one is difficult to drop

graphql-client is something we can't easily replace and control, so I suppose we can only keep using activesupport for now.

That said, it's only used in gitlab-triage, we don't necessarily use it in triage-ops web service, nor in the tests. We can still potentially isolate the dependency.

See !2464 (comment 1591077475)