Make icon appear for new preset animal=horse_walker always

[Hufkratzer]

A new preset openstreetmap/id-tagging-schema#1857 was merged, but it needs something to be done here so that the icon always appears. Currently the icon only appears if the tag animal=horse_walker is acompanied by some other tag like building=* or leisure=*, example here: https://ideditor.netlify.app/#disable_features=boundaries&map=21.00/50.76960/-2.20871&background=MAPNIK&id=w1347874758

The reason why this is so and what needs to be done was discussed here a bit:
openstreetmap/id-tagging-schema#1857 (comment) ff

[dheeraj12347]

Hi, I’d like to work on this issue.

From the discussion in the preset PR (#1857), it seems the icon does not appear because animal=horse_walker is not treated as an area feature unless another tag such as building=* is present. I’ll investigate the area/label logic in iD and see how we can ensure the icon appears consistently for this preset.

Please let me know if this approach sounds correct.