docs: Mark GL_KHR_no_error as done.

docs: Mark GL_KHR_no_error as done.

Drivers have supported KHR_no_error for a while.  We'd been leaving it
marked as "in progress" because there's a zillion places that could get
slightly more optimized.  But, Timothy and Samuel have already done
piles of work, and I think we have a solid implementation at this point.

Let's check it off the list.

Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>