[CI] Bump actions/checkout from 3 to 4

Bumps [actions/checkout](https://github.com/actions/checkout) from 3 to 4.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](actions/checkout@v3...v4)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/ci.yml

@@ -44,7 +44,7 @@ jobs:
  - os: macOS-latest
  ghc: 'latest'
  steps:
- - uses: actions/checkout@v3
+ - uses: actions/checkout@v4
  - uses: haskell/actions/setup@v2.4.1
  id: setup-haskell-cabal
  with: