Add spurge seeds

[Rail-Runner]

Summary

SUMMARY: Features "Add spurge seeds"

Purpose of change

Make recently-added plant replenishable, so that player won't run out of it if they stay in one place for a long time, and doesn't have to run around the wilderness to gather more.

I also wanted to add seeds for lotus plant too, but turns out they require rather unusual conditions to grow (that is, there has to be a layer of water where they're growing, with above-ground plant part floating on water) and currently those aren't supported properly, so I just removed generic "flower" seeds from its harvest entry.

Also remove the mention of burdock from wild herbs description, since it now exists as a separate item and plant.

Describe the solution

JSON editing.

Describe alternatives you've considered

Adding support for growing aquatic plants, like lotus is, though adding it for just one not-so-useful plant seems a bit much.

Testing

Not necessary; changes made are fairly straightforward.

Additional context

None.

[curstwist]

Don't forget to add to some item_groups for spawning.
ga_items_1 (community garden)
farming_seeds
trash

are all good choices.

[Rail-Runner]

Done.