Remove tests with obsolete "Handling scroll from main thread"

Made obsolete with the following CL:
http://crrev.com/c/2694007

Bug: 664858, 574283
Change-Id: I8d440917cde534b9ab54d185192990b962e634d8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5818691


Reviewed-by: Steve Kobes <skobes@chromium.org>
Commit-Queue: Adam Ettenberger <Adam.Ettenberger@microsoft.com>
Cr-Commit-Position: refs/heads/main@{#1349427}