Ensure exceeding max chunk size doesn't forbid splits

I was playing around with the buzhash implementation in this repo for https://github.com/aidanhs/rollsum-tests and I noticed that it seemed to be not working properly (would only generate a few chunks for a massive file, and the last chunk would be huge).

A look at the code revealed that the condition to split on hitting the max chunk size was effectively inverted, so once hitting the max chunk size it would never split!