Fix webpages_playback.py instructions

Bug: chromium:1482435
Change-Id: Ib189662ee78f0c1df20d68b5a92f72bac7ca1c36
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/755580
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
1 file changed