chore(deps): bump jontze/action-mdbook from 3 to 4

Bumps [jontze/action-mdbook](https://github.com/jontze/action-mdbook) from 3 to 4.
- [Release notes](https://github.com/jontze/action-mdbook/releases)
- [Changelog](https://github.com/jontze/action-mdbook/blob/master/CHANGELOG.md)
- [Commits](jontze/action-mdbook@v3...v4)

---
updated-dependencies:
- dependency-name: jontze/action-mdbook
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/book.yaml

@@ -32,7 +32,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v6
       - name: Install mdBook
-        uses: jontze/action-mdbook@v3
+        uses: jontze/action-mdbook@v4
         with:
           token: ${{ secrets.GITHUB_TOKEN }}
           mdbook-version: "~0.4.52" # mdbook 0.5 is not compatible with linkcheck and requires linkcheck2, see https://github.com/jontze/action-mdbook/issues/671