chore(deps): update davidanson/markdownlint-cli2-action action to v21

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
DavidAnson/markdownlint-cli2-action	action	major	v20 -> v21

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Release Notes

DavidAnson/markdownlint-cli2-action (DavidAnson/markdownlint-cli2-action)

v21

Compare Source

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Configuration

📅 Schedule: Branch creation - Between 12:00 AM and 03:59 AM, only on Monday ( * 0-3 * * 1 ) (UTC), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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• If you want to rebase/retry this PR, check this box

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