ci: bump peaceiris/actions-mdbook from v1 to v1.1.12 (#360)

Bumps [peaceiris/actions-mdbook](https://github.com/peaceiris/actions-mdbook) from v1 to v1.1.12.
- [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...95a4401)

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

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

.github/workflows/test.yml

@@ -79,7 +79,7 @@ jobs:
 
       - name: Setup mdBook
         if: github.ref == 'refs/heads/master'
-        uses: peaceiris/actions-mdbook@v1
+        uses: peaceiris/actions-mdbook@v1.1.12
         with:
           mdbook-version: '0.3.7'