Bump Microsoft.VisualStudio.Validation from 17.6.11 to 17.8.8 (#1230)

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
...

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

Directory.Packages.props

@@ -27,7 +27,7 @@
     <PackageVersion Include="Microsoft.VisualStudio.Interop" Version="17.4.33103.184" />
     <PackageVersion Include="Microsoft.VisualStudio.Shell.15.0" Version="17.4.33103.184" />
     <PackageVersion Include="Microsoft.VisualStudio.Shell.Framework" Version="17.4.33103.184" />
-    <PackageVersion Include="Microsoft.VisualStudio.Validation" Version="17.6.11" />
+    <PackageVersion Include="Microsoft.VisualStudio.Validation" Version="17.8.8" />
     <PackageVersion Include="Microsoft.Win32.Registry" Version="5.0.0" />
     <PackageVersion Include="Microsoft.Windows.CsWin32" Version="0.2.188-beta" />
     <PackageVersion Include="Nullable" Version="1.3.1" />