Improve danger rule FeatureCategorySuggestion

What does this MR do and why?

This MR addresses some pain points mentioned in #468847.

It:

• Makes suggestions more useful and actual suggest something
  • See https://gitlab.com/gitlab-org/gitlab/-/jobs/7184073259
  • !157346 (comment 1967054460)
  • !157346 (comment 1967054476)

• Skips danger spec rules whenever an MR is reverted
  • See https://gitlab.com/gitlab-org/gitlab/-/jobs/7184047673

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.