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

This MR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v3 -> v4

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Release Notes

actions/checkout

v4

Compare Source

• url-helper.ts now leverages well-known environment variables by @​jww3 in https://github.com/actions/checkout/pull/1941
• Expand unit test coverage for isGhes by @​jww3 in https://github.com/actions/checkout/pull/1946

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