unable to add/use Colortouch T7850

[craftyguy]

d2fe349 caused a regression on the Colortouch T7850, which doesn't support humidity control.

Traceback (most recent call last):
  File "/usr/src/homeassistant/homeassistant/components/venstar/config_flow.py", line 68, in async_step_user
    info = await validate_input(self.hass, user_input)
  File "/usr/src/homeassistant/homeassistant/components/venstar/config_flow.py", line 47, in validate_input
    info_success = await hass.async_add_executor_job(client.update_info)
  File "/usr/local/lib/python3.10/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/usr/local/lib/python3.10/site-packages/venstarcolortouch/venstarcolortouch.py", line 207, in update_info
    self.hum_setpoint = self.get_settings("hum_setpoint")
  File "/usr/local/lib/python3.10/site-packages/venstarcolortouch/venstarcolortouch.py", line 272, in get_settings
    setting = r.json()[attr]
KeyError: 'hum_setpoint'