Bump DavidAnson/markdownlint-cli2-action from 20.0.0 to 21.0.0 (#6344)

Author: dependabot[bot]

.github/workflows/lint.yml

@@ -29,7 +29,7 @@ jobs:
         with:
           persist-credentials: false
       - name: Lint
-        uses: DavidAnson/markdownlint-cli2-action@992badcdf24e3b8eb7e87ff9287fe931bcb00c6e # v20.0.0
+        uses: DavidAnson/markdownlint-cli2-action@30a0e04f1870d58f8d717450cc6134995f993c63 # v21.0.0
         with:
           globs: |
             CHANGELOG.md