[m-rev.] for post-commit review: use similar diagnostics for similar pragmas

[Julien Fischer]

On Mon, 15 Sept 2025 at 10:05, Zoltan Somogyi <zoltan.somogyi at runbox.com> wrote:
> Unify diagnostics for foreign_{,_export}_enum pragmas.
>
> compiler/add_foreign_enum.m:
> compiler/check_type_inst_mode_defns.m:
>     There used to be unnecessary differences between how we reported
>     foreign_enum and foreign_export_enum pragmas for non-enum du types.
>     Fir this by using the same code for reporting this problem for
>     both pragmas. Make this code use the best parts of each original approach.
>
> tests/invalid/ee_invalid.err_exp:
> tests/invalid/exported_foreign_enum.err_exp:
>     Expect the updated text.

That's fine.

Julien.