Update the CI script

[aantron]

• Build on OCaml 5 and 4.14.
• Relax the bugfix version (e.g. 4.13.x rather than 4.13.1.
• We probably don't need to build on every single version between 4.03 and 5.2.
• Use the latest actions/checkout and setup-ocaml.

See https://github.com/aantron/dream/blob/d0887715121217070d6a62f8ade1dd3d24cf8e96/.github/workflows/test.yml for reference.