Y24-244 - Update checkout dependency to v4

[SHIV5T3R]

Closes https://github.com/sanger/General-Backlog-Items/issues/433

Changes proposed in this pull request

• Bumped checkout dependency to v4.

Instructions for Reviewers

[All PRs] - Confirm PR template filled
[Feature Branches] - Review code
[Production Merges to main]
    - Check story numbers included
    - Check for debug code
    - Check version

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 77.98%. Comparing base (af0cd03) to head (7af8eb2). Report is 10 commits behind head on develop.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## develop #2064 +/- ## ======================================== Coverage 77.98% 77.98% ======================================== Files 471 471 Lines 17975 17975 Branches 262 262 ======================================== Hits 14018 14018 Misses 3955 3955 Partials 2 2 ``` | [Flag](https://app.codecov.io/gh/sanger/limber/pull/2064/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sanger) | Coverage Δ | | |---|---|---| | [javascript](https://app.codecov.io/gh/sanger/limber/pull/2064/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sanger) | `69.89% <ø> (ø)` | | | [pull_request](https://app.codecov.io/gh/sanger/limber/pull/2064/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sanger) | `77.98% <ø> (?)` | | | [push](https://app.codecov.io/gh/sanger/limber/pull/2064/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sanger) | `77.98% <ø> (ø)` | | | [ruby](https://app.codecov.io/gh/sanger/limber/pull/2064/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sanger) | `91.16% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=sanger#carryforward-flags-in-the-pull-request-comment) to find out more.

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[StephenHulme]

Looks good, but I think it needs a rebase