Bump step-security/harden-runner from 2.17.0 to 2.18.0

Bumps [step-security/harden-runner](https://github.com/step-security/harden-runner) from 2.17.0 to 2.18.0.
- [Release notes](https://github.com/step-security/harden-runner/releases)
- [Commits](step-security/harden-runner@f808768...6c3c2f2)

---
updated-dependencies:
- dependency-name: step-security/harden-runner
  dependency-version: 2.18.0
  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

@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@f808768d1510423e83855289c910610ca9b43176 # v2.17.0
+        uses: step-security/harden-runner@6c3c2f2c1c457b00c10c4848d6f5491db3b629df # v2.18.0
         with:
           egress-policy: audit