chore(deps): update xunit-dotnet monorepo to v2.8.1 (open-feature#266)

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This PR contains the following updates:

| Package | Change | Age | Adoption | Passing | Confidence |
|---|---|---|---|---|---|
| [xunit](https://github.com/xunit/xunit) | `2.7.1` -> `2.8.1` |
[![age](https://developer.mend.io/api/mc/badges/age/nuget/xunit/2.8.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/nuget/xunit/2.8.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/nuget/xunit/2.7.1/2.8.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![confidence](https://developer.mend.io/api/mc/badges/confidence/nuget/xunit/2.7.1/2.8.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
|
[xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit)
| `2.5.8` -> `2.8.1` |
[![age](https://developer.mend.io/api/mc/badges/age/nuget/xunit.runner.visualstudio/2.8.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![adoption](https://developer.mend.io/api/mc/badges/adoption/nuget/xunit.runner.visualstudio/2.8.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
[![passing](https://developer.mend.io/api/mc/badges/compatibility/nuget/xunit.runner.visualstudio/2.5.8/2.8.1?slim=true)](https://docs.renovatebot.com/merge-confidence/)
|
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|

---

### Release Notes

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

### [`v2.8.1`](https://github.com/xunit/xunit/compare/2.8.0...2.8.1)

[Compare Source](https://github.com/xunit/xunit/compare/2.8.0...2.8.1)

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

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

</details>

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

###
[`v2.8.1`](https://github.com/xunit/visualstudio.xunit/compare/2.8.0...2.8.1)

[Compare
Source](https://github.com/xunit/visualstudio.xunit/compare/2.8.0...2.8.1)

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

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

</details>

---

### Configuration

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are satisfied.

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rebase/retry checkbox.

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---

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---

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Directory.Packages.props

@@ -24,8 +24,8 @@
     <PackageVersion Include="SpecFlow" Version="3.9.74" />
     <PackageVersion Include="SpecFlow.Tools.MsBuild.Generation" Version="3.9.74" />
     <PackageVersion Include="SpecFlow.xUnit" Version="3.9.74" />
-    <PackageVersion Include="xunit" Version="2.7.1" />
-    <PackageVersion Include="xunit.runner.visualstudio" Version="2.5.8" />
+    <PackageVersion Include="xunit" Version="2.8.1" />
+    <PackageVersion Include="xunit.runner.visualstudio" Version="2.8.1" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(OS)' == 'Unix'">