Bump streetsidesoftware/cspell-action from 6.3.0 to 6.8.0

Bumps [streetsidesoftware/cspell-action](https://github.com/streetsidesoftware/cspell-action) from 6.3.0 to 6.8.0.
- [Release notes](https://github.com/streetsidesoftware/cspell-action/releases)
- [Changelog](https://github.com/streetsidesoftware/cspell-action/blob/main/CHANGELOG.md)
- [Commits](streetsidesoftware/cspell-action@v6.3.0...v6.8.0)

---
updated-dependencies:
- dependency-name: streetsidesoftware/cspell-action
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

.github/workflows/validate-documentation.yml

@@ -32,7 +32,7 @@ jobs:
         args: "--threads 1 --max-concurrency 1 --verbose --no-progress './**/*.md' './**/*.html'"
 
     - name: Run markdownlint
-      uses: streetsidesoftware/cspell-action@v6.3.0
+      uses: streetsidesoftware/cspell-action@v6.8.0
       with:
         files: '**/*.md'