Remove "~Accepting merge requests" label on all merge requests

Problem

The ~"Accepting merge requests" label is usually attached to issues that are marked as open for community contributions. However, it's also attached to merged requests opened directly from the issue using the dropdown option or using the quick actions. The label is also sometimes added manually on merge requests.

Proposal

1. Remove the ~"Accepting merge requests" label from all merge requests.
2. Add a policy rule for the @gitlab-bot to auto remove this label from future merge requests that will continue to attach that label due to current UX. There is probably no need to change the current UX since auto removing the automatically attached ~"Accepting merge requests" label would be unnecessarily too specific, right?