Backport "Fix environment scope regex" to CE

What does this MR do?

We fixed a "environment scope regex" problem https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3641 in EE. This problem happened in only EE, because the culprit affected only EE specific feature, "Enviroment-specific variables". However, we fixed shared parts instead of the specific code because of fixing route cause.

Therefore this patch is not Next Patch Release even though EE has the label.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Close https://gitlab.com/gitlab-org/gitlab-ee/issues/4308