Update actions/checkout action to v4

[renovate[bot]]

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

• Support fetching without the --progress option
• Update to node20

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Configuration

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