chore(deps): update xunit-dotnet monorepo to v2.8.0 (buehler#755)

[![Mend
Renovate](https://app.renovatebot.com/images/banner.svg)](https://renovatebot.com)

This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [xunit](https://togithub.com/xunit/xunit) | `2.7.1` -> `2.8.0` |
[![age](https://developer.mend.io/api/mc/badges/age/nuget/xunit/2.8.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/nuget/xunit/2.8.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/nuget/xunit/2.7.1/2.8.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/nuget/xunit/2.7.1/2.8.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
|
[xunit.runner.visualstudio](https://togithub.com/xunit/visualstudio.xunit)
| `2.5.8` -> `2.8.0` |
[![age](https://developer.mend.io/api/mc/badges/age/nuget/xunit.runner.visualstudio/2.8.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/nuget/xunit.runner.visualstudio/2.8.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/nuget/xunit.runner.visualstudio/2.5.8/2.8.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/nuget/xunit.runner.visualstudio/2.5.8/2.8.0?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|

---

### Release Notes

<details>
<summary>xunit/xunit (xunit)</summary>

### [`v2.8.0`](https://togithub.com/xunit/xunit/compare/2.7.1...2.8.0)

[Compare Source](https://togithub.com/xunit/xunit/compare/2.7.1...2.8.0)

</details>

<details>
<summary>xunit/visualstudio.xunit (xunit.runner.visualstudio)</summary>

###
[`v2.8.0`](https://togithub.com/xunit/visualstudio.xunit/compare/2.5.8...2.8.0)

[Compare
Source](https://togithub.com/xunit/visualstudio.xunit/compare/2.5.8...2.8.0)

</details>

---

### Configuration

📅 **Schedule**: Branch creation - "after 9pm,before 6am" in timezone
Europe/Zurich, Automerge - At any time (no schedule defined).

🚦 **Automerge**: Enabled.

♻ **Rebasing**: Whenever PR becomes conflicted, or you tick the
rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about these
updates again.

---

- [ ] <!-- rebase-check -->If you want to rebase/retry this PR, check
this box

---

This PR has been generated by [Mend
Renovate](https://www.mend.io/free-developer-tools/renovate/). View
repository job log
[here](https://developer.mend.io/github/buehler/dotnet-operator-sdk).

<!--renovate-debug:eyJjcmVhdGVkSW5WZXIiOiIzNy4zMjEuMiIsInVwZGF0ZWRJblZlciI6IjM3LjMyMS4yIiwidGFyZ2V0QnJhbmNoIjoibWFpbiIsImxhYmVscyI6WyJkZXBlbmRlbmNpZXMiXX0=-->

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

test/Directory.Build.props

@@ -11,8 +11,8 @@
     <ItemGroup>
         <PackageReference Include="FluentAssertions" Version="6.12.0" />
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
-        <PackageReference Include="xunit" Version="2.7.1" />
-        <PackageReference Include="xunit.runner.visualstudio" Version="2.5.8">
+        <PackageReference Include="xunit" Version="2.8.0" />
+        <PackageReference Include="xunit.runner.visualstudio" Version="2.8.0">
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
             <PrivateAssets>all</PrivateAssets>
         </PackageReference>