compositor: delete cms-static and cms-colord plugins

Plugins cms-static and cms-colord were deprecated with "compositor:
deprecate cms-static and cms-colord plugins", and the promise was that
we'd delete them if no one complained.

They were deprecated 2 years ago, and no one bothered. So it's about
time to delete them.

See #634

.

Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>