ci: bump peaceiris/actions-mdbook from v1.1.12 to v1.1.13 (#503)

Bumps [peaceiris/actions-mdbook](https://github.com/peaceiris/actions-mdbook) from v1.1.12 to v1.1.13.
- [Release notes](https://github.com/peaceiris/actions-mdbook/releases)
- [Changelog](https://github.com/peaceiris/actions-mdbook/blob/master/CHANGELOG.md)
- [Commits](peaceiris/actions-mdbook@v1.1.12...96256d8)

Signed-off-by: dependabot[bot] <[email protected]>

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

Author: dependabot[bot]

.github/workflows/test.yml

@@ -88,7 +88,7 @@ jobs:
 
       - name: Setup mdBook
         if: github.ref == 'refs/heads/main'
-        uses: peaceiris/[email protected].12
+        uses: peaceiris/[email protected].13
         with:
           mdbook-version: '0.3.7'