This script was broken for the last few days and I couldn't figure out why.
Turns out it was checking for the existence of a file that got renamed,
so rename it in here too.
Fixes: f926cf5b ("docs: Rename GL3.txt to features.txt")
CC: Ian Romanick <email@example.com>
CC: Rob Clark <firstname.lastname@example.org>
Signed-off-by: Eric Engestrom <email@example.com>
Signed-off-by: Rob Clark <firstname.lastname@example.org>