Bump step-security/harden-runner from 2.19.3 to 2.19.4 (#534)

Bumps [step-security/harden-runner](https://github.com/step-security/harden-runner) from 2.19.3 to 2.19.4.
- [Release notes](https://github.com/step-security/harden-runner/releases)
- [Commits](step-security/harden-runner@ab7a940...9af89fc)

---
updated-dependencies:
- dependency-name: step-security/harden-runner
  dependency-version: 2.19.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

.github/workflows/push_gem.yml

@@ -30,7 +30,7 @@ jobs:
 
     steps:
       - name: Harden Runner
-        uses: step-security/harden-runner@ab7a9404c0f3da075243ca237b5fac12c98deaa5 # v2.19.3
+        uses: step-security/harden-runner@9af89fc71515a100421586dfdb3dc9c984fbf411 # v2.19.4
         with:
           egress-policy: audit