Bump xunit (#42717)

Bumps the dotnet group in /samples/snippets/core/testing/unit-testing-best-practices/csharp with 1 update: [xunit](https://github.com/xunit/xunit).


Updates `xunit` from 2.9.0 to 2.9.1
- [Commits](xunit/xunit@2.9.0...2.9.1)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

samples/snippets/core/testing/unit-testing-best-practices/csharp/after/unit-testing-best-practices-after.csproj

@@ -9,7 +9,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
-    <PackageReference Include="xunit" Version="2.9.0" />
+    <PackageReference Include="xunit" Version="2.9.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
   </ItemGroup>
 

samples/snippets/core/testing/unit-testing-best-practices/csharp/before/unit-testing-best-practices-before.csproj

@@ -9,7 +9,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
-    <PackageReference Include="xunit" Version="2.9.0" />
+    <PackageReference Include="xunit" Version="2.9.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
   </ItemGroup>