Bump step-security/harden-runner from 2.8.1 to 2.9.1

Bumps [step-security/harden-runner](https://github.com/step-security/harden-runner) from 2.8.1 to 2.9.1.
- [Release notes](https://github.com/step-security/harden-runner/releases)
- [Commits](step-security/harden-runner@17d0e2b...5c7944e)

---
updated-dependencies:
- dependency-name: step-security/harden-runner
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/push_gem.yml

@@ -22,7 +22,7 @@ jobs:
     steps:
       # Set up
       - name: Harden Runner
-        uses: step-security/harden-runner@17d0e2bd7d51742c71671bd19fa12bdc9d40a3d6 # v2.8.1
+        uses: step-security/harden-runner@5c7944e73c4c2a096b17a9cb74d65b6c2bbafbde # v2.9.1
         with:
           egress-policy: audit