docs: add missing )

TBR=hans@chromium.org

Bug: 
Change-Id: I6ad83952a2d5a670ba772c8c671d8cc3e040b507
Reviewed-on: https://chromium-review.googlesource.com/733872
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510889}
1 file changed