Bump JamesIves/github-pages-deploy-action from 4.6.3 to 4.6.8

Bumps [JamesIves/github-pages-deploy-action](https://github.com/jamesives/github-pages-deploy-action) from 4.6.3 to 4.6.8.
- [Release notes](https://github.com/jamesives/github-pages-deploy-action/releases)
- [Commits](JamesIves/github-pages-deploy-action@v4.6.3...v4.6.8)

---
updated-dependencies:
- dependency-name: JamesIves/github-pages-deploy-action
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

.github/workflows/publish.yaml

@@ -21,7 +21,7 @@ jobs:
         run: cd docs && mdbook build && touch book/.nojekyll
 
       - name: Publish documentation
-        uses: JamesIves/github-pages-deploy-action@v4.6.3
+        uses: JamesIves/github-pages-deploy-action@v4.6.8
         with:
           branch: gh-pages
           folder: docs/book/