Fix #13: move UpdateAdaptiveQuality() to LateUpdate.

[TrebuhD]

Fix the adaptive quality screen flicker bug by moving UpdateAdaptiveQuality() from OnPreCull() to LateUpdate() in ValveCamera.cs, as suggested by @Selkcip.

[SpencerMalone]

I still get a "jump" anytime it changes quality. Is that to be expected? Seems like not.

[SpencerMalone]

I guess it's not every time it changes quality, but there is certainly an increase in the lurches that I get.

[Selkcip]

Is it hitching or are you seeing a skewed frame? This won't fix occasional hitching, but does fix a serious bug where a single, very obvious, frame would be rendered with the wrong viewport dimensions making things unplayable.

[SpencerMalone]

It was hitching, as it turns out. Not sure if it was reimporting the assets or bumping up my unity version, but one of the two solved it. I think I was getting hitching+the frame thing before, and this definitely fixed the frame badness, but left the hitching (because it was my fault 😿 ). Anyways, this LGTM!

[mikejichaow]

it does fixed flickering by moving UpdateAdaptiveQuality(); to lateupdate.