Replace amenity=dog_park with leisure=dog_park

[SomeoneElseOSM]

Currently https://shortbread-tiles.org/schema/1.1/#layer-pois says it contains amenity=dog_park, but presumably this is a typing error for leisure=dog_park. See https://taginfo.openstreetmap.org/search?q=dog_park#values - 6 of the latter, 27k of the former. 4 of the 6 .amenity=dog_park are also tagged leisure=dog_park

Since this is a bugfix rather than a feature it could go in 1.1, and perhaps even 1.0.