Bump xunit from 2.7.0 to 2.8.0

Bumps [xunit](https://github.com/xunit/xunit) from 2.7.0 to 2.8.0.
- [Commits](xunit/xunit@2.7.0...2.8.0)

---
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]

BitFaster.Caching.UnitTests/BitFaster.Caching.UnitTests.csproj

@@ -13,7 +13,7 @@
     <PackageReference Include="FluentAssertions" Version="6.12.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageReference Include="Moq" Version="4.20.69" />
-    <PackageReference Include="xunit" Version="2.7.0" />
+    <PackageReference Include="xunit" Version="2.8.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>