Remove NOTIFICATION_EXTENSION_PAGE_ACTIONS_UPDATED
We're trying to kill off notifications, and this one's no
different.
Also, move the logic for notifying the location bar of
page actions being updated to ExtensionActionAPI.
BUG=
406590
Committed:
https://crrev.com/aeffd18ea04d1bdfc141383d547e1fe7494bb691
Cr-Commit-Position: refs/heads/master@{#291920}