Unclear documentation for bpm_at

[garcia]

simfile/simfile/timing/engine.py

Line 283 in caacf9c

A note is considered "unhittable" if and only if:

I phrased this weirdly; at minimum, it should say "if and only if either of these conditions hold true". But there's probably a better way to phrase it to begin with.

[garcia]

I don't see the issue with this line anymore, not sure why it was bugging me.