py3-gpiozero: need py3-colorzero dependency
gpiozero now depends on colorzero, gpiozero will fail on import with ModuleNotFoundError: No module named 'colorzero'
if it is not present.
See https://github.com/gpiozero/gpiozero/blob/70cc7725d51142ed7343f94a42d70727e44f6f6f/setup.py#L58.
colorzero's homepage: https://github.com/waveform80/colorzero.