Get rid of unsafe variables.

lib/pleroma/web/activity_pub/mrf/simple_policy.ex

lib/pleroma/web/activity_pub/transmogrifier.ex

lib/pleroma/web/activity_pub/views/user_view.ex

lib/pleroma/web/mastodon_api/mastodon_api_controller.ex

lib/pleroma/web/web_finger/web_finger.ex