Bump Microsoft.VisualStudio.Validation from 17.6.11 to 17.8.8 (#716)

Bumps [Microsoft.VisualStudio.Validation](https://github.com/microsoft/vs-validation) from 17.6.11 to 17.8.8.
- [Release notes](https://github.com/microsoft/vs-validation/releases)
- [Commits](https://github.com/microsoft/vs-validation/commits)

---
updated-dependencies:
- dependency-name: Microsoft.VisualStudio.Validation
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Directory.Packages.props

@@ -18,7 +18,7 @@
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageVersion Include="Microsoft.VisualStudio.Threading.Analyzers" Version="$(VSThreadingVersion)" />
     <PackageVersion Include="Microsoft.VisualStudio.Threading" Version="$(VSThreadingVersion)" />
-    <PackageVersion Include="Microsoft.VisualStudio.Validation" Version="17.6.11" />
+    <PackageVersion Include="Microsoft.VisualStudio.Validation" Version="17.8.8" />
     <PackageVersion Include="NSubstitute" Version="5.1.0" />
     <PackageVersion Include="NSubstitute.Analyzers.CSharp" Version="1.0.16" />
     <PackageVersion Include="PInvoke.Kernel32" Version="0.7.124" />