Tweak sitemaps docs
|Reported by:||Adam Vandenberg||Owned by:||nobody|
|Cc:||Triage Stage:||Ready for checkin|
|Has patch:||yes||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
Changed an awkward phrase and capitalized "Google" in a doc-comment.
(I also think the "ping Google on model save" example is not a great idea, but felt weird about just removing it.)