The `hmi` repository is meant to be used on targets, so `-dev` packages
aren't needed there.

At the moment we are not testing anywhere that the `-dev` packages are still
installable when the `:development` repository is enabled, but that scenario
is arguably covered by the builds on OBS.

The broken chain is:

* mildenhall-dev
* libmildenhall-0-dev
* libgrassmoor-dev
* libclutter-1.0-dev
* libatk1.0-dev
* pkg-config

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>