On Debian, `rust-coreutils` is meant to be installed alongside
`coreutils`, which would cause file conflicts if the manpages had the
same name, hence the need for the `rust-` prefix.

We intend to fully replace `coreutils` with `rust-coreutils` in Apertis,
so this prefix is not necessary nor relevant in our case.

Signed-off-by: Arnaud Ferraris <arnaud.ferraris@collabora.com>