Bump xunit from 2.5.0 to 2.5.1

Bumps [xunit](https://github.com/xunit/xunit) from 2.5.0 to 2.5.1.
- [Commits](xunit/xunit@2.5.0...2.5.1)

---
updated-dependencies:
- dependency-name: xunit
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

test/HtmlSanitizer.Tests/HtmlSanitizer.Tests.csproj

@@ -39,7 +39,7 @@
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers</IncludeAssets>
     </PackageReference>
-    <PackageReference Include="xunit" Version="2.5.0" />
+    <PackageReference Include="xunit" Version="2.5.1" />
     <PackageReference Include="System.Text.Encoding.CodePages">
       <Version>7.0.0</Version>
     </PackageReference>