Update SecondaryGoogleAccountSigninAllowed policy's documentation

With Chrome OS Account Manager enabled,
SecondaryGoogleAccountSigninAllowed applies to the unified account list
in Chrome OS Account Manager, and not just Chrome content area, as the
policy documentation claims.

Update the documentation to reflect this fact.

Another related policy: AllowedDomainsForApps does not require any
change.

Bug: 967206
Change-Id: Ifde3d6c8a68fb2ec22006bb4cdcc1b0707f15351
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1768464
Reviewed-by: Bartosz Fabianowski <bartfab@chromium.org>
Commit-Queue: Kush Sinha <sinhak@chromium.org>
Cr-Commit-Position: refs/heads/master@{#690333}
1 file changed