Number of temporal layers in screen sharing was unintentionally changed
from 3 to 2 in a796a7ee85b8805a92e21f888a893bef1581bfee.
This changes the value to 3.
Bug: webrtc:9013
Change-Id: I68291b49276afd2689f20d1c3581e149aa6fd610
Reviewed-on: https://webrtc-review.googlesource.com/61860
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22621}