"404 no such service or method" when setting Picture Mode
Hello!

First of all, thanks for creating and maintaining this amazing plugin.

My setup works great so far, but I can't get the picture mode changed. Similar issue to #375 but in my case the setting doesn't even change in first place.

I am running webOS 3 and LG software version 05.60.15.

Debug log says:

```
[12/7/2021, 11:05:49 PM] [webostv] [My LG TV] system.notifications service - createAlert requested. Title: lunaSend, Message: lunaSend, Type: confirm, Modal: true
[12/7/2021, 11:05:49 PM] [webostv] [My LG TV] Message from TV 

[12/7/2021, 11:05:49 PM] [webostv] [My LG TV]  {
  type: 'utf8',
  utf8Data: '{"type":"error","id":"<scrubbed>","error":"404 no such service or method","payload":{}}'
}
[12/7/2021, 11:05:49 PM] [webostv] [My LG TV] Unknown error while requesting createAlert from service system.notifications
[12/7/2021, 11:05:49 PM] [webostv] [My LG TV] system.notifications service - createAlert requested. Title: lunaSend, Message: lunaSend, Type: confirm, Modal: true
[12/7/2021, 11:05:49 PM] [webostv] [My LG TV] Message from TV 

[12/7/2021, 11:05:49 PM] [webostv] [My LG TV]  {
  type: 'utf8',
  utf8Data: '{"type":"error","id":"<scrubbed>","error":"404 no such service or method","payload":{}}'
}
[12/7/2021, 11:05:49 PM] [webostv] [My LG TV] Unknown error while requesting createAlert from service system.notifications
[12/7/2021, 11:05:49 PM] [webostv] [My LG TV] Remote input socket - sending command: ENTER
```
Any idea what I am dealing with here? Happy to send a PR, but not sure if this is simply a compatibility issue with my TV which was purchased around 2016.