Bump DavidAnson/markdownlint-cli2-action from 17 to 18 (#1558)

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

Author: dependabot[bot]

.github/workflows/markdownlint.yml

@@ -31,7 +31,7 @@ jobs:
         files: 'content/**/*.md'
         separator: "\n"
 
-    - uses: DavidAnson/markdownlint-cli2-action@v17
+    - uses: DavidAnson/markdownlint-cli2-action@v18
       if: steps.changed-files.outputs.any_changed == 'true'
       with:
         globs: ${{ steps.changed-files.outputs.all_changed_files }}