chore(deps): bump xunit from 2.8.1 to 2.9.0

Bumps xunit from 2.8.1 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>

Author: dependabot[bot]

tests/Microsoft.Graph.DotnetCore.Core.Test/Microsoft.Graph.DotnetCore.Core.Test.csproj

@@ -25,7 +25,7 @@
     </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.10.0" />
     <PackageReference Include="Moq" Version="4.20.70" />
-    <PackageReference Include="xunit" Version="2.8.1" />
+    <PackageReference Include="xunit" Version="2.9.0" />
     <ProjectReference Include="..\..\src\Microsoft.Graph.Core\Microsoft.Graph.Core.csproj" />
   </ItemGroup>
    <ItemGroup>