Fix extraneous parenthesis in WPT docs

Also edit a couple words.

Bug: 
Change-Id: I1398aac2be37aa2902a0def6892ad273946eb178
Reviewed-on: https://chromium-review.googlesource.com/752060
Reviewed-by: Quinten Yearsley <qyearsley@chromium.org>
Commit-Queue: Jeff Carpenter <jeffcarp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513629}
1 file changed