Bump step-security/harden-runner from 2.14.1 to 2.15.0 (#117)

Bumps [step-security/harden-runner](https://github.com/step-security/harden-runner) from 2.14.1 to 2.15.0.
- [Release notes](https://github.com/step-security/harden-runner/releases)
- [Commits](step-security/harden-runner@e3f713f...a90bcbc)

---
updated-dependencies:
- dependency-name: step-security/harden-runner
  dependency-version: 2.15.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/push_gem.yml

@@ -23,7 +23,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@e3f713f2d8f53843e71c69a996d56f51aa9adfb9 # v2.14.1
+        uses: step-security/harden-runner@a90bcbc6539c36a85cdfeb73f7e2f433735f215b # v2.15.0
         with:
           egress-policy: audit