libobs: Increase async jitter compensation

Due to the fact that async timestamps themselves can be susceptible to
minor jitter from certain types of inputs, increase the allowable jitter
compensation value to ensure that the rendered frame timing from async
video sources is always as close as possible to the compositor.

When the framerate of the source is the same as the framerate as the
compositor, this (combined with the fact that clamped video timing now
being used with async video frames) helps ensure that buffered async
video sources will sync up their rendering to the compositor as
accurately as possible despite jitter from the source's timestamps.

If there is no jitter in the source's timestamps then it'll always sync
up perfectly with the compositor, thanks to clamped video timing.