Dangerfile: Add group labels
When an MR is created, we can automatically add group::gitaly based on the mr author. Additionally, we can inherit gitaly::cluster and gitaly::git labels as well from the linked issue.
e5e9234f (danger: Remove tracking of team members, 2021-12-17) had removed this because it was a static list that would easily grow stale. Now that we are pulling from the group, that mitigates the staleness risk.
This is important for reporting purposes, and is related to https://gitlab.com/gitlab-com/gitlab-OKRs/-/work_items/124562951
fixes: #5026 (closed)
Edited by John Cai