Bump multidict from 4.7.6 to 5.0.0 (#531)

Bumps [multidict](https://github.com/aio-libs/multidict) from 4.7.6 to 5.0.0.
<details>
<summary>Release notes</summary>
<p><em>Sourced from <a href="https://github.com/aio-libs/multidict/releases">multidict's releases</a>.</em></p>
<blockquote>
<h2>multidict 5.0.0</h2>
<h2>Features</h2>
<ul>
<li>Provide wheels for <code>aarch64</code>, <code>i686</code>, <code>ppc64le</code>, <code>s390x</code> architectures on Linux
as well as <code>x86_64</code>.
<code>[#500](aio-libs/multidict#500) &lt;https://github.com/aio-libs/multidict/issues/500&gt;</code>_</li>
<li>Provide wheels for Python 3.9.
<code>[#534](aio-libs/multidict#534) &lt;https://github.com/aio-libs/multidict/issues/534&gt;</code>_</li>
</ul>
<h2>Removal</h2>
<ul>
<li>Drop Python 3.5 support; Python 3.6 is the minimum supported Python version.</li>
</ul>
<h2>Misc</h2>
<ul>
<li><code>[#503](aio-libs/multidict#503) &lt;https://github.com/aio-libs/multidict/issues/503&gt;</code>_</li>
</ul>
</blockquote>
</details>
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a href="https://github.com/aio-libs/multidict/blob/master/CHANGES.rst">multidict's changelog</a>.</em></p>
<blockquote>
<h1>5.0.0 (2020-10-12)</h1>
<h2>Features</h2>
<ul>
<li>Provide wheels for <code>aarch64</code>, <code>i686</code>, <code>ppc64le</code>, <code>s390x</code> architectures on Linux as well as <code>x86_64</code>. <a href="https://github-redirect.dependabot.com/aio-libs/multidict/issues/500">#500</a></li>
<li>Provide wheels for Python 3.9. <a href="https://github-redirect.dependabot.com/aio-libs/multidict/issues/534">#534</a></li>
</ul>
<h2>Removal</h2>
<ul>
<li>Drop Python 3.5 support; Python 3.6 is the minimal supported Python version.</li>
</ul>
<h2>Misc</h2>
<ul>
<li><a href="https://github-redirect.dependabot.com/aio-libs/multidict/issues/503">#503</a></li>
</ul>
<hr />
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a href="https://github.com/aio-libs/multidict/commit/087f9dcb4b880409a4a9a8f59ded15b1d6b90513"><code>087f9dc</code></a> Fix artifacts path</li>
<li><a href="https://github.com/aio-libs/multidict/commit/421de960a06a58996fd9558b4fe98ee78ffb2617"><code>421de96</code></a> Fix artifacts path</li>
<li><a href="https://github.com/aio-libs/multidict/commit/2b22b2c47b2a881335c688577a6dbd7ab5c06558"><code>2b22b2c</code></a> Fix manylinux build</li>
<li><a href="https://github.com/aio-libs/multidict/commit/eea466d174b52b94312b8e99ffdcca4fff9cd6c2"><code>eea466d</code></a> Fix tests</li>
<li><a href="https://github.com/aio-libs/multidict/commit/001ae3b33c370b8cb29740f7ff05e3b28efaa5c0"><code>001ae3b</code></a> Fix spelling</li>
<li><a href="https://github.com/aio-libs/multidict/commit/e152be053ff91d80fdabf6f1d9be3f4bd095c20f"><code>e152be0</code></a> Update whitelist</li>
<li><a href="https://github.com/aio-libs/multidict/commit/a02e976ff173b377f30a09b1a021a1c8a81d4594"><code>a02e976</code></a> Bump to 5.0.0</li>
<li><a href="https://github.com/aio-libs/multidict/commit/d41493d3a477f50af370a2e52fcb99222902cb4e"><code>d41493d</code></a> Bump mypy version</li>
<li><a href="https://github.com/aio-libs/multidict/commit/9a70da9c9679f466989e44e18a4f11589e7725b7"><code>9a70da9</code></a> Drop azure-pipelines integration</li>
<li><a href="https://github.com/aio-libs/multidict/commit/5fb74cfac3963580113bf7d1e2d3a70ec45af3db"><code>5fb74cf</code></a> Final deployment</li>
<li>Additional commits viewable in <a href="https://github.com/aio-libs/multidict/compare/v4.7.6...v5.0.0">compare view</a></li>
</ul>
</details>
<br />


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requirements/test.txt

@@ -1,6 +1,6 @@
 pytest-cov>=2.3.1
 pytest==6.1.1
-multidict==4.7.6
+multidict==5.0.0
 idna==2.10
 typing_extensions==3.7.4.2;python_version<"3.8"
 -e .