Bump xunit from 2.8.0 to 2.9.1 (#1794)

Bumps [xunit](https://github.com/xunit/xunit) from 2.8.0 to 2.9.1.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/xunit/xunit/commit/bb7c3e4e7435b20d627b3babdf2c5681e4ad7b22"><code>bb7c3e4</code></a>
v2.9.1</li>
<li><a
href="https://github.com/xunit/xunit/commit/5d70d25462492a6ee67664da468b99a624550e01"><code>5d70d25</code></a>
<a href="https://redirect.github.com/xunit/xunit/issues/3028">#3028</a>:
Support IGrouping&lt;TKey,TValue&gt; in Assert.Equivalent (v2)</li>
<li><a
href="https://github.com/xunit/xunit/commit/ed6e05b57ef61441dbe85475001083321a2c84b6"><code>ed6e05b</code></a>
Add support for IGrouping&lt;,&gt; in ArgumentFormatter, assuming it's
safe to re-e...</li>
<li><a
href="https://github.com/xunit/xunit/commit/d97c7f863d8caa88813f940786b97b7c98ae4f52"><code>d97c7f8</code></a>
Restore TestInvoker&lt;T&gt;.GetTaskFromResult (forwards to
AsyncUtility.TryConvert...</li>
<li><a
href="https://github.com/xunit/xunit/commit/416ed8182d9b6a4a712563e6d7519a7c8281588e"><code>416ed81</code></a>
<a href="https://redirect.github.com/xunit/xunit/issues/3021">#3021</a>:
Add overload of Assert.Equal to resolve compiler ambiguity</li>
<li><a
href="https://github.com/xunit/xunit/commit/6b86235b1b2fa3bda92be6dde1cca389d72f1278"><code>6b86235</code></a>
Add Assert.Equivalent support for evaluating Lazy&lt;T&gt;</li>
<li><a
href="https://github.com/xunit/xunit/commit/aadff058f0bd74e1ce12f69d7c021902167966b1"><code>aadff05</code></a>
Updated build table in README</li>
<li><a
href="https://github.com/xunit/xunit/commit/1949c7816895e976bb3f40878fb82b0b3e7764f8"><code>1949c78</code></a>
Missing &lt;properties&gt; wrapper in JUnit output</li>
<li><a
href="https://github.com/xunit/xunit/commit/7dceffaa263958f296f86222bdd4ccad89fd35d4"><code>7dceffa</code></a>
<a href="https://redirect.github.com/xunit/xunit/issues/2979">#2979</a>:
Update JUnitXml.xslt, based on <a
href="https://github.com/testmoapp/junitxml?t">https://github.com/testmoapp/junitxml?t</a>...</li>
<li><a
href="https://github.com/xunit/xunit/commit/935af73407795a3c77bf3d7a4a3b464a3fa394f2"><code>935af73</code></a>
Latest assertion tests</li>
<li>Additional commits viewable in <a
href="https://github.com/xunit/xunit/compare/2.8.0...2.9.1">compare
view</a></li>
</ul>
</details>
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Directory.Packages.props

@@ -28,7 +28,7 @@
     <PackageVersion Include="System.Security.Cryptography.Algorithms" Version="4.3.1" />
     <PackageVersion Include="System.Xml.ReaderWriter" Version="4.3.1" />
     <PackageVersion Include="System.ValueTuple" Version="4.5.0" />
-    <PackageVersion Include="xunit" Version="2.8.0" />
+    <PackageVersion Include="xunit" Version="2.9.1" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.8.1" />
   </ItemGroup>
 </Project>