[openweathermap] Finish clean-up & Fix OneCall Forecast Thing channel creation (...

[openweathermap] Finish clean-up & Fix OneCall Forecast Thing channel creation (#16416)

* [openweathermap] Clean-Up config.xml

Remove config description for removed UV Index Thing.

* [openweathermap] Fix OneCall Thing creates to many channels

The default setting is to create 0 minutes, 12 hours and 6 days of forecast channels.
When creating a new OneCall Thing, actually 60 minutes, 24 hours and 8 days of forecast were created due to the thing-types, but those not needed (as determined by the configuration) were not removed.

Signed-off-by: Florian Hotze <florianh_dev@icloud.com>