Add Gitea URL-scheme fix references

[cookesan]

Adds Gitea URL-scheme fix references to GHSA-hq57-c72x-4774.

Audit refresh, July 8, 2026:

• Confirmed the live PR is open, ready for review, merge-clean, and the visible advisory check is green.
• Rechecked the merge-base diff: exactly one advisory JSON file changes (advisories/github-reviewed/2025/12/GHSA-hq57-c72x-4774/GHSA-hq57-c72x-4774.json), JSON parses, git diff --check passes, and the exact-head worktree is clean.
• Revalidated the added public references in the diff; all resolve through their source site or registry.

[cookesan]

Refreshed on July 8, 2026:

• GHSA-hq57-c72x-4774 and CVE-2025-68946 remain public and consistent with this advisory.
• Verified go-gitea/gitea PRs #25960 and #25964, commit ab54310731411c09ff41b8eb75eb6a3691768d06, release v1.20.1, and the Go module proxy record for code.gitea.io/gitea v1.20.1.
• Local validation passed: jq empty and git diff --check.

No affected range, package, or severity changes are included.