Audit activity-stream for network requests

In ff68 there are some snippets network requests coming from activity stream (re[/activity-stream/lib/ASRouter.jsm).](/activity-stream/lib/ASRouter.jsm`).) We should make sure to disable these and any other related background requests.

Some relevant prefs: https://github.com/ghacksuserjs/ghacks-user.js/blob/a92c4086bbf8c4324c4369d1dc8a39338334af45/user.js#L109