chore(ci): drop the actionlint $/ ignore once upstream ships support (rhysd/actionlint#711/#732)

Once actionlint ships support for GitHub's self-repository uses: $/... syntax (upstream tracking: rhysd/actionlint#711, rhysd/actionlint#732 — both open as of 2026-09-19; latest release v1.7.12 predates the syntax), the scoped stopgap added in #6622 should be removed.

What to remove: the args: ['--ignore=reusable workflow call "\$/.*is not following the format'] line (and its comment block) on the actionlint hook in .pre-commit-config.yaml.

Why it exists: actionlint v1.7.9 (CI-pinned, frozen rev) rejects every valid $/ ref as a malformed workflow-call, so pre-commit ignores exactly that one message, anchored both on the $/ ref prefix and the format-message wording. Verified at the time: all 40 valid refs suppressed; a malformed remote ref (missing @ref) and future $/ diagnostic shapes still fail.

Acceptance:

• Bump the actionlint hook rev to a release with $/ support, delete the ignore line, and run pre-commit run actionlint --all-files — must be clean with no ignore.
• Bonus while there: check whether the new version existence-checks $/ callees; if it does, the repo-wide pass in check-release-gate-needs.py (check_local_workflow_refs) becomes redundant and could be simplified.

Context: #6622 (40 refs converted across 6 workflow files), zizmor self-repository alerts #8218–#8257.