Remove support for surface=paving_stones:30 and surface=paving_stones:20

[mkoniecz]

This values are problematic: they mix basic surface type with extreme detail (size of paving stone)

See ​https://wiki.openstreetmap.org/wiki/Tag%3Asurface%3Dpaving_stones%3A30 and ​https://community.openstreetmap.org/t/paving-stones-30-en-gebruik/104143 and ​https://taginfo.openstreetmap.org/tags/surface=paving_stones%3A30#chronology

For :20 variant see ​https://taginfo.openstreetmap.org/tags/surface=paving_stones%3A20#overview

Note that this preset had some questionable surface values, fixed in https://josm.openstreetmap.de/wiki/Presets/MountainbikeTrails?action=diff&version=7

I can make this edit on my own but it goes beyond "obvious typo" and into "this tagging schema is a bad idea, I want it to be eradicated"

[taylor.smock]

See comment:39:ticket:21396.

We already have a validator check that warns about it (see source:trunk/resources/data/validator/highway.mapcss@19028:211-217#L211​ ).

[skyper]

The values were added by anonymous nine years ago.

+1. for removing.

[stoecker]

+1 for removing.

[mkoniecz]

https://josm.openstreetmap.de/wiki/Presets/MountainbikeTrails?action=diff&version=8