dim: Fix url_to_remote

The regex in

Author: Emil Velikov <emil.velikov@collabora.com>
Date:   Wed Oct 24 15:22:08 2018 +0100

    dim: handle repo URLs ending with forward slash

didn't actually work. Fix it.

Cc: Emil Velikov <emil.velikov@collabora.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>