Updater: update test documentation to account for new paths, wakes.

Change-Id: I117825ed7c0cf8716de5ee3df47ee3d70aa2ee30
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4226764


Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
Auto-Submit: Joshua Pawlicki <waffles@chromium.org>
Reviewed-by: Xiaoling Bao <xiaolingbao@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1102448}