Bumps the xunit group with 5 updates:

| Package | From | To |
| --- | --- | --- |
| [xunit](https://github.com/xunit/xunit) | `2.6.5` | `2.7.0` |
| [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) | `2.5.6` | `2.5.7` |
| [Verify.Xunit](https://github.com/VerifyTests/Verify) | `22.11.4` | `23.7.1` |
| [System.Collections.Immutable](https://github.com/dotnet/runtime) | `1.5.0` | `8.0.0` |
| [System.Threading.Tasks.Extensions](https://github.com/dotnet/corefx) | `4.5.0` | `4.5.4` |


Updates `xunit` from 2.6.5 to 2.7.0
- [Commits](xunit/xunit@2.6.5...2.7.0)

Updates `xunit.runner.visualstudio` from 2.5.6 to 2.5.7
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.6...2.5.7)

Updates `Verify.Xunit` from 22.11.4 to 23.7.1
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](VerifyTests/Verify@22.11.4...23.7.1)

Updates `System.Collections.Immutable` from 1.5.0 to 8.0.0
- [Release notes](https://github.com/dotnet/runtime/releases)
- [Commits](https://github.com/dotnet/runtime/commits/v8.0.0)

Updates `System.Threading.Tasks.Extensions` from 4.5.0 to 4.5.4
- [Release notes](https://github.com/dotnet/corefx/releases)
- [Commits](https://github.com/dotnet/corefx/commits)

---
updated-dependencies:
- dependency-name: xunit
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: xunit
- dependency-name: xunit.runner.visualstudio
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: xunit
- dependency-name: Verify.Xunit
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: xunit
- dependency-name: System.Collections.Immutable
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: xunit
- dependency-name: System.Threading.Tasks.Extensions
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: xunit
...

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

This is unneeded since v23.0.0
https://github.com/VerifyTests/Verify/milestone/312