build(deps): bump Xunit.SkippableFact from 1.3.12 to 1.4.8 (#573)

Bumps [Xunit.SkippableFact](https://github.com/AArnott/Xunit.SkippableFact) from 1.3.12 to 1.4.8.
- [Release notes](https://github.com/AArnott/Xunit.SkippableFact/releases)
- [Commits](AArnott/Xunit.SkippableFact@v1.3.12...v1.4.8)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

src/Akavache.Tests/Akavache.Tests.csproj

@@ -12,7 +12,7 @@
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.console" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.1" />
-    <PackageReference Include="Xunit.SkippableFact" Version="1.3.12" />
+    <PackageReference Include="Xunit.SkippableFact" Version="1.4.8" />
     <PackageReference Include="Xunit.StaFact" Version="0.3.18" />
     <PackageReference Include="ReactiveUI.Testing" Version="11.*" />
     <PackageReference Include="Splat" Version="9.*" />