Bump System.IO.Abstractions from 21.0.29 to 21.2.1

Bumps [System.IO.Abstractions](https://github.com/TestableIO/System.IO.Abstractions) from 21.0.29 to 21.2.1.
- [Release notes](https://github.com/TestableIO/System.IO.Abstractions/releases)
- [Commits](TestableIO/System.IO.Abstractions@v21.0.29...v21.2.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Fritz.StreamTools/Fritz.StreamTools.csproj

@@ -33,7 +33,7 @@
 		<PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="8.0.5" />
 		<PackageReference Include="Octokit" Version="0.50.0" />
 		<PackageReference Include="System.Formats.Asn1" Version="8.0.1" />
-		<PackageReference Include="System.IO.Abstractions" Version="21.0.29" />
+		<PackageReference Include="System.IO.Abstractions" Version="21.2.1" />
 		<PackageReference Include="System.Memory" Version="4.6.0" />
 		<PackageReference Include="System.Net.Security" Version="4.3.2" />
 		<PackageReference Include="System.Text.RegularExpressions" Version="4.3.1" />