Update Node.js to v21 - autoclosed

This MR contains the following updates:

Package	Type	Update	Change
node	final	major	18-alpine -> 21-alpine
node	final	major	16-alpine -> 21-alpine

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Release Notes

nodejs/node (node)

v21

Moved to doc/changelogs/CHANGELOG_V4.md#4.2.6.

v20

Moved to doc/changelogs/CHANGELOG_V012.md#0.12.14.

v19

Moved to doc/changelogs/CHANGELOG_IOJS.md#1.6.0.

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Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

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

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

🔕 Ignore: Close this MR and you won't be reminded about these updates again.

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