Default/flowers: Improve papyrus and waterlily schematics

Papyrus:
Make base node dirt instead of dirt_with_grass. Formerly the exposed
dirt would change to grass but the new grass spread ABM now prevents that.

Waterlily:
Don't specify a water_source node in the schematic, as it may be used in
river water. It was not force-placed but should really be "air" prob = 0.