Improve ring-doorbell CLI help texts

[cpina]

(ring_doorbell) carles@pinux:~/.venvs$ ring-doorbell --help
[...]
  listen            Listen to push notification like the ones sent to...
  motion-detection  Display ring devices.
  show              Display ring devices.
  videos            Interact with ring videos.

I think that the help text might be wrong or incorrect. I don't have any ring device so I cannot properly test it at the moment.

I've found it while writing a manual page.

[github-actions]

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