Bump virtualenv from 20.13.3 to 20.13.4 in /.github/workflows (#240)

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.13.3 to 20.13.4.
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a href="https://github.com/pypa/virtualenv/blob/20.13.4/docs/changelog.rst">virtualenv's changelog</a>.</em></p>
<blockquote>
<h2>v20.13.4 (2022-03-18)</h2>
<p>Bugfixes - 20.13.4</p>
<pre><code>- Improve performance of python startup inside created virtualenvs - by :user:`asottile`. (`[#2317](pypa/virtualenv#2317) &lt;https://github.com/pypa/virtualenv/issues/2317&gt;`_)
- Upgrade embedded setuptools to ``60.10.0`` from ``60.9.3`` - by :user:`gaborbernat`. (`[#2320](pypa/virtualenv#2320) &lt;https://github.com/pypa/virtualenv/issues/2320&gt;`_)
</code></pre>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/pypa/virtualenv/commit/775c1893e555139a9fbe7429c04062f4904afbe8"><code>775c189</code></a> release 20.13.4</li>
<li><a href="https://github.com/pypa/virtualenv/commit/63c94afc2487013b49cd816ccbde854bda85688d"><code>63c94af</code></a> Bump setuptools (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2320">#2320</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/a16f609ec9ff6797d7694591151371c51698d911"><code>a16f609</code></a> fix 20ms startup penalty added by virtualenv (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2317">#2317</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/d865c3e2940f287b065a4071cac59f543a2b23be"><code>d865c3e</code></a> [pre-commit.ci] pre-commit autoupdate (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2318">#2318</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/4d1176c2602f880c64b488a0e7cc24db89da2424"><code>4d1176c</code></a> Merge pull request <a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2312">#2312</a> from pypa/release-20.13.3</li>
<li>See full diff in <a href="https://github.com/pypa/virtualenv/compare/20.13.3...20.13.4">compare view</a></li>
</ul>
</details>
<br />


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</details>

.github/workflows/constraints.txt

@@ -2,4 +2,4 @@ pip==22.0.4
 nox==2022.1.7
 nox-poetry==0.9.0
 poetry==1.1.13
-virtualenv==20.13.3
+virtualenv==20.13.4