fix api url for planetspotters.net

[zivillian]

this fixes the planespotters.net images for planes which have no icao code in their database but have images like the german military NH90 with registration 79+23

[wiedehopf]

too many wrong pictures, that's why the code exists in the first place.

[zivillian]

Do you have an example, where this returns a wrong image? Maybe I can come up with a better solution.

[wiedehopf]

This is the request it makes: https://api.planespotters.net/pub/photos//hex/3F9E5B?reg=79+23&icaoType=NH90

It's what we agreed on with planespotters.
It should be ok to only match the registration and still return something, feel free to contact planespotters about this.