Bump xunit.runner.visualstudio from 2.5.8 to 2.8.0 in /gremlin-dotnet

Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.5.8 to 2.8.0.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](https://github.com/xunit/visualstudio.xunit/compare/2.5.8...2.8.0)

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

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