github: [skip ci]: bump DavidAnson/markdownlint-cli2-action

Bumps [DavidAnson/markdownlint-cli2-action](https://github.com/davidanson/markdownlint-cli2-action) from 19 to 20.
- [Release notes](https://github.com/davidanson/markdownlint-cli2-action/releases)
- [Commits](https://github.com/davidanson/markdownlint-cli2-action/compare/v19...v20)

---
updated-dependencies:
- dependency-name: DavidAnson/markdownlint-cli2-action
  dependency-version: '20'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/build.yml

@@ -25,7 +25,7 @@ jobs:
           files: |
              **.md
           since_last_remote_commit: true
-      - uses: DavidAnson/markdownlint-cli2-action@v19
+      - uses: DavidAnson/markdownlint-cli2-action@v20
         with:
           config: .markdownlint-cli2.yaml
           globs: ${{ steps.changed-markdown-files.outputs.all_changed_files }}