Update actions/checkout action to v4

[mend-for-github-com[bot]]

This PR contains the following updates:

Package	Type	Update	Change
actions/checkout	action	major	v2 -> v4

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Release Notes

actions/checkout (actions/checkout)

### [`v4`](https://redirect.github.com/actions/checkout/blob/HEAD/CHANGELOG.md#v422) [Compare Source](https://redirect.github.com/actions/checkout/compare/v3...v4) - `url-helper.ts` now leverages well-known environment variables by [@​jww3](https://redirect.github.com/jww3) in [https://github.com/actions/checkout/pull/1941](https://redirect.github.com/actions/checkout/pull/1941) - Expand unit test coverage for `isGhes` by [@​jww3](https://redirect.github.com/jww3) in [https://github.com/actions/checkout/pull/1946](https://redirect.github.com/actions/checkout/pull/1946) ### [`v3`](https://redirect.github.com/actions/checkout/blob/HEAD/CHANGELOG.md#v360) [Compare Source](https://redirect.github.com/actions/checkout/compare/v2...v3) - [Fix: Mark test scripts with Bash'isms to be run via Bash](https://redirect.github.com/actions/checkout/pull/1377) - [Add option to fetch tags even if fetch-depth > 0](https://redirect.github.com/actions/checkout/pull/579)

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