Update dependency xunit to 2.9.1

Author: renovate[bot]

Source/Cake.DotNetVersionDetector.Tests/Cake.DotNetVersionDetector.Tests.csproj

@@ -19,7 +19,7 @@
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>
     <PackageReference Include="NSubstitute" Version="5.1.0" />
-    <PackageReference Include="xunit" Version="2.9.0" />
+    <PackageReference Include="xunit" Version="2.9.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>