Refactor remove approvers if not used
<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=428854) </details> <!--IssueSummary end--> The `ee/app/models/concerns/approval_rule_like.rb` file contains an `approvers` method that does not appear to be called anymore so it should be removed The following discussion from !134108 should be addressed: - [ ] @terrichu started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/134108#note_1607626753): (+1 comment) > **question (non-blocking):** Can this method now be removed? I don't know this area of code well. Perhaps better to be explored in a follow up
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