Assign a responsible developer for plinko-probability

[pixelzoom]

In 1e25039 on 4/26/23, responsibility for plinko-probability was transferred from @chrisklus to @pixelzoom. I was not aware of this. I already have too many sims that I'm responsible for, so I'm not interested in assuming ownership. I'll update responsibile_dev.json to point to this issue, and assign this issue to @kathy-phet to choose another developer.