hoon: clarify comments for +rep:in and +rep:by
hoon: clarify comments for +rep:in and +rep:by

"Replace" suggests this function either produces an updated set/map when done,
like +snap, or changes all values in-place, like +turn. In truth, it's more
similar to +roll, which does reduction/accumulation.

("Reduce" specifically was chosen because it maintains the mnemonic relation to
the arm name.)
ngzax/urbit,urbit/urbit,jfranklin9000/urbit,ngzax/urbit,jfranklin9000/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,jfranklin9000/urbit,urbit/urbit,ngzax/urbit,urbit/urbit,jfranklin9000/urbit,jfranklin9000/urbit,urbit/urbit,urbit/urbit,ngzax/urbit,ngzax/urbit,jfranklin9000/urbit,ngzax/urbit,jfranklin9000/urbit