chore(deps): bump peaceiris/actions-mdbook from 1 to 2 (#362)

Bumps [peaceiris/actions-mdbook](https://github.com/peaceiris/actions-mdbook) from 1 to 2.
- [Release notes](https://github.com/peaceiris/actions-mdbook/releases)
- [Changelog](https://github.com/peaceiris/actions-mdbook/blob/main/CHANGELOG.md)
- [Commits](peaceiris/actions-mdbook@v1...v2)

---
updated-dependencies:
- dependency-name: peaceiris/actions-mdbook
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/docs.yml

@@ -42,7 +42,7 @@ jobs:
           directory: ${{ runner.temp }}/llvm-${{ matrix.clang }}
           cached: ${{ steps.cache-llvm.outputs.cache-hit }}
       - name: Install mdbook
-        uses: peaceiris/actions-mdbook@v1
+        uses: peaceiris/actions-mdbook@v2
         with:
           mdbook-version: ${{ matrix.mdbook }}
       - name: Build guide