Bump System.IO.Abstractions from 21.2.1 to 21.2.8

Bumps [System.IO.Abstractions](https://github.com/TestableIO/System.IO.Abstractions) from 21.2.1 to 21.2.8.
- [Release notes](https://github.com/TestableIO/System.IO.Abstractions/releases)
- [Commits](TestableIO/System.IO.Abstractions@v21.2.1...v21.2.8)

---
updated-dependencies:
- dependency-name: System.IO.Abstractions
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

Directory.Packages.props

@@ -22,7 +22,7 @@
     <PackageVersion Include="NUnit.Analyzers" Version="4.6.0" />
     <PackageVersion Include="SecurityCodeScan.VS2019" Version="5.6.7" />
     <PackageVersion Include="SixLabors.ImageSharp" Version="3.1.6" />
-    <PackageVersion Include="System.IO.Abstractions" Version="21.2.1" />
+    <PackageVersion Include="System.IO.Abstractions" Version="21.2.8" />
     <PackageVersion Include="System.IO.FileSystem" Version="4.3.0" />
     <PackageVersion Include="Terminal.Gui" Version="1.17.1" />
     <PackageVersion Include="YamlDotNet" Version="16.2.1" />