Bump virtualenv from 20.8.1 to 20.9.0 in /.github/workflows (#68)

Bumps [virtualenv](https://github.com/pypa/virtualenv) from 20.8.1 to 20.9.0.
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a href="https://github.com/pypa/virtualenv/blob/main/docs/changelog.rst">virtualenv's changelog</a>.</em></p>
<blockquote>
<h2>v20.9.0 (2021-10-23)</h2>
<p>Features - 20.9.0</p>
<pre><code>- Special-case ``--prompt .`` to the name of the current directory - by :user:`rkm`. (`[#2220](pypa/virtualenv#2220) &lt;https://github.com/pypa/virtualenv/issues/2220&gt;`_)
- Add libffi-8.dll to pypy windows `[#2218](pypa/virtualenv#2218) &lt;https://github.com/pypa/virtualenv/issues/2218&gt;`_ - by :user:`mattip`
<p>Bugfixes - 20.9.0
</code></pre></p>
<ul>
<li>Fixed path collision that could lead to a PermissionError or writing to system
directories when using PyPy3.8 - by :user:<code>mgorny</code>. (<code>[#2182](pypa/virtualenv#2182) &lt;https://github.com/pypa/virtualenv/issues/2182&gt;</code>_)</li>
<li>Upgrade embedded setuptools to <code>58.3.0</code> from <code>58.1.0</code> and pip to <code>21.3.1</code> from <code>21.2.4</code> - by
:user:<code>gaborbernat</code>. (<code>[#2205](pypa/virtualenv#2205) &lt;https://github.com/pypa/virtualenv/issues/2205&gt;</code>_)</li>
<li>Remove stray closing parenthesis in activate.bat - by :user:<code>SiggyBar</code>. (<code>[#2221](pypa/virtualenv#2221) &lt;https://github.com/pypa/virtualenv/issues/2221&gt;</code>_)</li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/pypa/virtualenv/commit/35d6a19dad02c5b9d4f700f3aaf9cbecb284cbb6"><code>35d6a19</code></a> release 20.9.0</li>
<li><a href="https://github.com/pypa/virtualenv/commit/4a1328b8f764683bffe860cd34ab0510f6e790d7"><code>4a1328b</code></a> Bump pip and setuptools (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2222">#2222</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/6bfc29e1a3d621e3f622a0d0395ff261ce0f3973"><code>6bfc29e</code></a> special-case <code>--prompt .</code> to the cwd (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2220">#2220</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/4188ac6e72d3b731595c83d46d1c0eb76fe4f6eb"><code>4188ac6</code></a> Support PyPy 3.8 (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2206">#2206</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/35ec4416d2012cfcb7a5e638813f6d52e852f29f"><code>35ec441</code></a> Remove stray closing parenthesis in activate.bat (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2221">#2221</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/c36117987cf65da92d4cfa7ab042f28a6266e135"><code>c361179</code></a> add libffi-8.dll to pypy windows _shared_libs (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2218">#2218</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/c77c6bc30edde2885091ad0945a093638ecbf45a"><code>c77c6bc</code></a> refactor to not do too much in ReentrantFileLock.<strong>del</strong> (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2213">#2213</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/6633e8578f65dd8f5eced14b9f6a7a495e55389a"><code>6633e85</code></a> Fix feature request template (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2217">#2217</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/df8e5f29939258913817b47bb5c01767fc333cd5"><code>df8e5f2</code></a> Setup Githug workflow concurrency (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2212">#2212</a>)</li>
<li><a href="https://github.com/pypa/virtualenv/commit/eafadce95da65f29a94b2b3b732f3f95c6d8421d"><code>eafadce</code></a> [pre-commit.ci] pre-commit autoupdate (<a href="https://github-redirect.dependabot.com/pypa/virtualenv/issues/2211">#2211</a>)</li>
<li>Additional commits viewable in <a href="https://github.com/pypa/virtualenv/compare/20.8.1...20.9.0">compare view</a></li>
</ul>
</details>
<br />


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.github/workflows/constraints.txt

@@ -2,4 +2,4 @@ pip==21.3.1
 nox==2021.10.1
 nox-poetry==0.8.6
 poetry==1.1.11
-virtualenv==20.8.1
+virtualenv==20.9.0