Grant LUCI access to view all accounts

As per step 4.5 in:
go/luci/newroot/getting_started/4_change_verification?var.recipe-repo=build&var.recipe-host=go&var.main-source-repo=go&var.gob-host=go&var.project-id=go#grant-your-service-account-read-access-to-your-gerrit-repo

Change-Id: I242fe24c82d02704af832e1c1c384c49b5826a47
Reviewed-on: https://go-review.googlesource.com/c/All-Projects/+/471755
Reviewed-by: Heschi Kreinick <heschi@google.com>