Move js-emails-disabled to a better test locator
The following discussion from !98547 should be addressed: - [ ] @mrincon started a [discussion](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/98547#note_1149576804): (+1 comment) > **Suggestion (non-blocking):** This was not introduced here but `js-emails-disabled` should be replaced with a `data-testid` because it is only used in tests. > > Even then I suspect an improvement that find the checkbox by text label would be better because we ["recommend that you query by the element’s text label instead of by ID, class name, or data-testid."](https://docs.gitlab.com/ee/development/testing_guide/best_practices.html#ui-testing)
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