The actions/cache step pinned commit 27d5ce7 (= tag v5.0.5) but the
trailing comment read "# v5". The v5 moving tag points to a different
commit, so the comment was untruthful and zizmor flagged it as
ref-version-mismatch. Update the comment to the exact version the SHA
resolves to, matching the exact-version pin convention used elsewhere
(e.g. actions/checkout # v6.0.3).
Resolves code-scanning alert #2552
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>