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/build.yml

@@ -14,7 +14,7 @@ jobs:
         ocaml_version: ['default']
       fail-fast: false  # don't stop jobs if one fails
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
       - uses: coq-community/docker-coq-action@v1
         with:
           opam_file: 'coq-coqprime.opam'