Bump xunit from 2.5.3 to 2.6.0 (#1582)

Bumps [xunit](https://github.com/xunit/xunit) from 2.5.3 to 2.6.0.
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/xunit/xunit/commit/6a07b9530d643f938287db600feb46082e894188"><code>6a07b95</code></a>
v2.6.0</li>
<li><a
href="https://github.com/xunit/xunit/commit/5a7297e8dcbc7998dc85708af8fb3756888ccd14"><code>5a7297e</code></a>
<a href="https://redirect.github.com/xunit/xunit/issues/2806">#2806</a>:
Performance improvements in Assert.Equal (v2)</li>
<li><a
href="https://github.com/xunit/xunit/commit/a6b5cc4a9c218a8f063807f233dcdaeb28572d00"><code>a6b5cc4</code></a>
Add net6.0 binary to xunit.assert</li>
<li><a
href="https://github.com/xunit/xunit/commit/abc1dd3ba18ae60bd2d19af3eb1b80d250090e76"><code>abc1dd3</code></a>
Update Microsoft.NETCore.App.Ref to 6.0</li>
<li><a
href="https://github.com/xunit/xunit/commit/52b6638e6e454beeb46b037a2de5928d47c4c6e8"><code>52b6638</code></a>
Move CA1304 and CA1305 enablement to production code only (not test
code)</li>
<li><a
href="https://github.com/xunit/xunit/commit/e139d771c23f4b53f2bae3f3437b778d5b8d3ba9"><code>e139d77</code></a>
Ensure all throws of NotImplementedException contain messages</li>
<li><a
href="https://github.com/xunit/xunit/commit/8a84fdb3eac52500f12c13897a931857da23ff70"><code>8a84fdb</code></a>
Ensure all GetHashCode functions are implemented (<a
href="https://redirect.github.com/xunit/xunit/issues/2804">#2804</a>)
(v2)</li>
<li><a
href="https://github.com/xunit/xunit/commit/c8532052c3c2454c35cb3e599f1c324c803659a5"><code>c853205</code></a>
Unit tests for <a
href="https://redirect.github.com/xunit/xunit/issues/2803">#2803</a>
(v2)</li>
<li><a
href="https://github.com/xunit/xunit/commit/8ffe56ac15a785434a7042acbabb33256000a477"><code>8ffe56a</code></a>
Unit tests for <a
href="https://redirect.github.com/xunit/xunit/issues/2800">#2800</a>
(v2)</li>
<li><a
href="https://github.com/xunit/xunit/commit/b2e660e51a924a42f85c48c4220712fd9c05d122"><code>b2e660e</code></a>
Replace (most) concatenation and interpolation (in shipped code) with
String....</li>
<li>Additional commits viewable in <a
href="https://github.com/xunit/xunit/compare/2.5.3...2.6.0">compare
view</a></li>
</ul>
</details>
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ImperatorToCK3.UnitTests/ImperatorToCK3.UnitTests.csproj

@@ -18,7 +18,7 @@
     </PackageReference>
     <PackageReference Include="FluentAssertions" Version="6.12.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
-    <PackageReference Include="xunit" Version="2.5.3" />
+    <PackageReference Include="xunit" Version="2.6.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>