The patch note is pretty much a summary, so go read that.

We're finding a happy medium here for Kha'Zix (and Rengar) in their ability to frontload damage as they come hurtling through the air to cuddle with the backline. This probably won't be the end of our Kha'Zix conversation, but we're currently being very, very careful with assassin tuning.

W - Void Spike

NEW BUFFERING BUGS Can now be 'buffered' mid-jump so that Kha'Zix can cast it slightly before landing

DATA QUEUE If Kha'Zix attempts to cast both Void Spikes and Void Assault while mid-air, he'll buffer only the last one he attempted to cast (not both, that would be too much)

R - Void Assault

NEW BUFFERING BUGS Can now be 'buffered' mid-jump so that Kha'Zix can cast it slightly before landing