fix(CI): Use OCaml 4.14.2 for Makefile tests

[bclement-ocp]

No description provided.

[Halbaroth]

I hesitated to bump the minimal OCaml version as you did. The only reason for which we need OCaml >= 4.14 is because the latest version of js_zarith_stubs as such a requirement but this package isn't a dependency of Alt-Ergo itself. I believe no ones use the AE js worker but us.

[bclement-ocp]

This does not bump the minimal OCaml version, it only changes the version that is only used on the CI to test the "Make all" target. Version constraints are unchanged, and we are still otherwise testing OCaml 4.08 / 4.14 / 5.0.

[Halbaroth]

By bumping the minimal version, I meant bumping the minimal version tested by the CI.
If we still test OCaml 4.08 on the CI for the binary and the library, I agree ;)

[bclement-ocp]

Yes — the change only concerns the "Make all" workflow (which simply checks that we can build using make); it does not apply to the other workflows (those that actually run the tests) as they use a different matrix!