Cannot remove "incident" label from incident issues
### Summary The Incident label cannot be removed from an issue once it has been added once. ### Steps to reproduce 1. ~~Add the incident label~~ 1. Create an incident issue (manually via `New Incident` or automatically via Alert Management) 2. Try to remove it by clicking on the x close to the label under the labels section on the right side of the web UI 3. The label is marked as removed on the issue activity but effectively remains there ![image](/uploads/2c07b01e7e232370f4725261140e82be/image.png) ### What is the current *bug* behavior? Please see https://gitlab.gnome.org/Infrastructure/GitLab/-/issues/463 for the exact behavior. #### Results of GitLab environment info <details> <summary>Expand for output related to GitLab environment info</summary> [gitlab_env.log](/uploads/020c3ccdc16d85bba790d2be799b5cc3/gitlab_env.log) </details> #### Results of GitLab application Check <!-- Input any relevant GitLab application check information if needed. --> <details> <summary>Expand for output related to the GitLab application check</summary> [gitlab_check.log](/uploads/a0102e5c01a9c4fa0f9b315271d6a682/gitlab_check.log) </details> ### Proposal for fixing This behavior is in place because we currently lack an `issue type` filter for the issue list page - without the labels, you can't surface incidents in the issue list. That is being fixed as part of https://gitlab.com/gitlab-org/gitlab/-/issues/268152. When that is completed, we can: 1. Allow people to remove the ~incident label 1. ~~STOP automatically applying the ~incident label to new incidents - this happens when incidents are created manually AND automatically by the GitLab Alert Bot.~~ We will do this after https://gitlab.com/gitlab-org/gitlab/-/issues/268152 is completed, but we can do the first step now. ### Technical proposal Removing the caller of [`Issues::BaseServce#add_incident_label`](https://gitlab.com/gitlab-org/gitlab/-/merge_requests/41598/diffs#03b07e4b5fcacb03a596088300ac1182968d7e3c_64_68) during update should stop (re-)adding the `~incident` label.
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