Bump xunit.core from 2.7.1 to 2.8.0

Bumps [xunit.core](https://github.com/xunit/xunit) from 2.7.1 to 2.8.0.
- [Commits](xunit/xunit@2.7.1...2.8.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

src/xRetry/xRetry.csproj

@@ -8,7 +8,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="xunit.core" Version="2.7.1" />
+    <PackageReference Include="xunit.core" Version="2.8.0" />
   </ItemGroup>
 
 </Project>