Allow tracktype=grade2 together with surface=ground

[Nekzuris]

I don't think surface=ground is incompatible with tracktype=grade2.

According to the wiki, grade2 is mostly solid and without grass in the middle.
The appropriate surface is often compacted but that is always a bit subjective, I use it when material has been added and worked on by machine, but sometimes the road is simply the natural ground that has been naturally compacted over time with regular use.
For that I use surface=ground because it's not dirt and I think it's more precise than unpaved, it's also not grade3 because there is no grass in the middle.

https://osmose.openstreetmap.fr/en/issue/fb90e4da-ead7-b7d4-ada9-c574b6e84f4f

[frodrigo]

This issue come from by a JOSM validator
https://josm.openstreetmap.de/browser/josm/trunk/resources/data/validator/combinations.mapcss

And has to be reported to JOSM.

[Nekzuris]

Done https://josm.openstreetmap.de/ticket/24070
And I would also remove ice and salt.