Update pre-commit hook DavidAnson/markdownlint-cli2 to v0.21.0

| datasource  | package                      | from    | to      |
| ----------- | ---------------------------- | ------- | ------- |
| github-tags | DavidAnson/markdownlint-cli2 | v0.18.1 | v0.21.0 |


Signed-off-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.pre-commit-config.yaml

@@ -25,7 +25,7 @@ repos:
       - id: gitleaks
 
   - repo: https://github.com/DavidAnson/markdownlint-cli2
-    rev: v0.18.1
+    rev: v0.21.0
     hooks:
       - id: markdownlint-cli2