Stop requiring permission to set region=None in search (bug 975413)

https://bugzilla.mozilla.org/show_bug.cgi?id=975413

Per comment 1 on this bug, we no longer need the `Regions:BypassFilters` to test payments in fireplace (I'm tempted to also remove the option in fireplace, but waiting to hear comments on this pull request first).

Since we ultimately want fireplace to be able to call search API completely anonymously, I felt the simplest thing to do was to remove the extra checks here. I don't think it hurts us much to let people do this kind of searches, but r- if you disagree :)