Issue cannot promote to epic if moved to promote to different group

Problem

1. Decided to promote this issue to an epic
2. Promoted epic could not accept issues in the groups we need to work in
3. Closed that epic, re-opened original issue
4. Moved original issue to an issue in a project where promotion would place the epic in the right spot
5. Tried to promote, cannot promote new issue to epic.

Potential Solution

Per #341630 (comment 685850946), maybe when we move issues we should clear promoted_to_epic_id out under some conditions (e.g. we change groups).