Deprecate and remove the 'Leading Organization' label
## Summary
The Leading Organizations program has been discontinued. The `Leading Organization` label is no longer being applied to new MRs (triage-ops automation removed in gitlab-org/quality/triage-ops!3931).
This issue tracks deprecating and eventually removing the label from `gitlab-org`.
## Context
The Leading Organizations program recognized organizations contributing 20+ merged MRs in the last 3 months with a dedicated review-response SLO. The program has been replaced by the unified contributor program.
## Related work
This is part of a chain removing all Leading Organizations references. Merge order: 1 → 2 → 3 → 4.
| # | Repo | What | Link | Status |
|---|------|------|------|--------|
| 1 | `gitlab-com/content-sites/handbook` | Remove from DevRel-owned pages | gitlab-com/content-sites/handbook!19000 | Open |
| 2 | `gitlab-com/content-sites/handbook` | Remove from Engineering-owned pages | gitlab-com/content-sites/handbook!19002 | Open |
| 3 | `gitlab-org/quality/triage-ops` | Remove labeler, detector, weekly report, CI job | gitlab-org/quality/triage-ops!3931 | Open |
| 4 | `gitlab-org/gitlab` | **This issue**: Deprecate `Leading Organization` label | #594277 | Open |
## What remains
- ~"Leading Organization" label exists on hundreds of historical MRs. The label provides useful historical signal for contribution tracking.
- The label definition still exists in the gitlab-org group label settings.
## Proposal
1. After the triage-ops MR merges: no new MRs will receive the label.
2. Keep the label on historical MRs (do not bulk-remove).
3. Remove the label definition from the group settings after a transition period (suggest end of FY26-Q1).
issue