chore(deps): update actions/setup-node action to v6

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	New value	References	Sourcegraph
actions/setup-node	action	major	v6	source

Test plan: CI should pass with updated dependencies. No review required: this is an automated dependency update PR.

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Release Notes

actions/setup-node (actions/setup-node)

v6

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v5

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v4

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v3

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Configuration

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♻ 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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