Bump DavidAnson/markdownlint-cli2-action from 17 to 18

Bumps [DavidAnson/markdownlint-cli2-action](https://github.com/davidanson/markdownlint-cli2-action) from 17 to 18.
- [Release notes](https://github.com/davidanson/markdownlint-cli2-action/releases)
- [Commits](DavidAnson/markdownlint-cli2-action@v17...v18)

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

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

.github/workflows/e3sm-gh-md-linter.yml

@@ -27,7 +27,7 @@ jobs:
       with:
         files: '**/*.md'
         separator: ","
-    - uses: DavidAnson/markdownlint-cli2-action@v17
+    - uses: DavidAnson/markdownlint-cli2-action@v18
       if: steps.changed-files.outputs.any_changed == 'true'
       with:
         config: 'docs/.markdownlint.json'