chore(dev-tools): update davidanson/markdownlint-cli2 (non-major)

Author: ppat-self-hosted-renovate-bot[bot]

.pre-commit-config.yaml

@@ -24,7 +24,7 @@ repos:
   - id: yamllint
     args: [--strict]
 - repo: https://github.com/DavidAnson/markdownlint-cli2
-  rev: v0.20.0
+  rev: v0.21.0
   hooks:
   - id: markdownlint-cli2
     args: ["--fix", "--config", ".markdownlint-cli2.yaml"]