A breaking API change broke the `policies/label-accepting-merge-requests.yml` policy

A breaking change to the Issues and MRs API was introduced and reported in https://gitlab.com/gitlab-org/gitlab-ce/issues/65676.

This in turn made our policies/label-accepting-merge-requests.yml policy apply the ~"Accepting merge requests" to a lot of issues that don't have a milestone, where normally they shouldn't (as we target issues with a milestone only).

A fix is in preparation to prevent that from happening while the API issue is fixed and deployed, and to revert the mistakenly added labels: !233 (closed)