ci: bump peaceiris/actions-mdbook from 1 to 1.1.14 (#384)

Bumps [peaceiris/actions-mdbook](https://github.com/peaceiris/actions-mdbook) from 1 to 1.1.14.
- [Release notes](https://github.com/peaceiris/actions-mdbook/releases)
- [Changelog](https://github.com/peaceiris/actions-mdbook/blob/main/CHANGELOG.md)
- [Commits](v1...v1.1.14)

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

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

.github/workflows/test-action.yml

@@ -22,7 +22,7 @@ jobs:
       - uses: actions/checkout@v2
 
       - name: Setup mdBook
-        uses: peaceiris/actions-mdbook@v1
+        uses: peaceiris/actions-mdbook@v1.1.14
         with:
           mdbook-version: ${{ matrix.mdbook-version }}