Bump DavidAnson/markdownlint-cli2-action from 20 to 21

Bumps [DavidAnson/markdownlint-cli2-action](https://github.com/davidanson/markdownlint-cli2-action) from 20 to 21.
- [Release notes](https://github.com/davidanson/markdownlint-cli2-action/releases)
- [Commits](DavidAnson/markdownlint-cli2-action@v20...v21)

---
updated-dependencies:
- dependency-name: DavidAnson/markdownlint-cli2-action
  dependency-version: '21'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/lint.yml

@@ -21,7 +21,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - name: Run markdownlint
-        uses: DavidAnson/markdownlint-cli2-action@v20
+        uses: DavidAnson/markdownlint-cli2-action@v21
 
   actionlint:
     name: action

.github/workflows/markdown.yml

@@ -19,7 +19,7 @@ jobs:
     steps:
       - uses: actions/checkout@v5
       - name: Run markdownlint
-        uses: DavidAnson/markdownlint-cli2-action@v20
+        uses: DavidAnson/markdownlint-cli2-action@v21
         with:
           globs: |
             *.md