[m-rev.] for review: remove obsoleted interface files

[Julien Fischer]

On Wed, 1 Dec 2021, Zoltan Somogyi wrote:

> Remove obsoleted interface files.
> 
> compiler/write_module_interface_files.m:
>     When we get errors that prevent us from constructing a new valid version
>     of an interface file, delete both
>
>     - any existing copy of that interface file to prevent its now-outdated info
>       from causing misleading error messages when compiling other modules, and
>
>     - any existing copy of its timestamp file, to prevent the build system
>       from executing any commands that need the now-deleted interface file.

That's fine.

Julien.