chore(deps): update actions/checkout action to v4

[renovate]

This PR contains the following updates:

Package	Type	Update	New value	References	Sourcegraph
actions/checkout	action	major	v4	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/checkout (actions/checkout)

v4

Compare Source

• Check out other refs/* by commit if provided, fall back to ref by @​orhantoy in https://github.com/actions/checkout/pull/1924

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