Prefer to use after_transition

What does this MR do?

Before_transition does not play nice when used with OptimisticLocking and this can result in triggering multiple events.

EE version: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/8839

What are the relevant issue numbers?

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/55306

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Tested in all supported browsers
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer