Bump step-security/harden-runner from 2.19.3 to 2.19.4 (ruby#1720)

Bumps
[step-security/harden-runner](https://github.com/step-security/harden-runner)
from 2.19.3 to 2.19.4.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a
href="https://github.com/step-security/harden-runner/releases">step-security/harden-runner's
releases</a>.</em></p>
<blockquote>
<h2>v2.19.4</h2>
<h2>What's Changed</h2>
<ul>
<li>Improvements for HTTPS Monitoring for the Enterprise tier of Harden
Runner</li>
</ul>
<p><strong>Full Changelog</strong>: <a
href="https://github.com/step-security/harden-runner/compare/v2.19.3...v2.19.4">https://github.com/step-security/harden-runner/compare/v2.19.3...v2.19.4</a></p>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/step-security/harden-runner/commit/9af89fc71515a100421586dfdb3dc9c984fbf411"><code>9af89fc</code></a>
Merge pull request <a
href="https://redirect.github.com/step-security/harden-runner/issues/667">#667</a>
from step-security/update-agent-v1.8.6</li>
<li><a
href="https://github.com/step-security/harden-runner/commit/485dce8cb5d75cda51e8bfa947de06030d080208"><code>485dce8</code></a>
Update agent to v1.8.6</li>
<li>See full diff in <a
href="https://github.com/step-security/harden-runner/compare/ab7a9404c0f3da075243ca237b5fac12c98deaa5...9af89fc71515a100421586dfdb3dc9c984fbf411">compare
view</a></li>
</ul>
</details>
<br />


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.github/workflows/push_gem.yml

@@ -23,7 +23,7 @@ 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