plainbox-provider-checkbox should depend on python3-guacamole

[Daniel Manrique]

Some scripts recently added to the checkbox provider (dkms_info, recovery_info) require guacamole to work, however, the provider itself doesn't depend on guacamole.

So I installed plainbox-provider-checkbox and canonical-hw-collection and when trying to run the collection whitelist (canonical-hw-collection-offline), two jobs crashed due to inability to load guacamole.

I'm not even sure that plainbox-provider-checkbox is the one that should depend on guacamole; however I'm pretty sure we want providers to depend on everything that their scripts need to at least run.