Bump xunit from 2.7.0 to 2.9.0

Bumps xunit from 2.7.0 to 2.9.0.

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

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

Bi5.Net.Tests/Bi5.Net.Tests.csproj

@@ -14,7 +14,7 @@
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
         <PackageReference Include="NSubstitute" Version="5.1.0" />
         <PackageReference Include="System.Linq.Async" Version="6.0.1" />
-        <PackageReference Include="xunit" Version="2.7.0" />
+        <PackageReference Include="xunit" Version="2.9.0" />
         <PackageReference Include="xunit.runner.visualstudio" Version="2.5.7">
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
             <PrivateAssets>all</PrivateAssets>