Allow all users to view and edit artist entries and wiki pages belonging
to banned artists. There was little need to hide these pages from
Members, it was mainly to appease artists who didn't like us even
linking to their sites.
These restrictions also had multiple flaws:
* Banned artist information was still visible in the API.
* It was still possible to edit banned artists using the API.
* It was still possible for unprivileged users to revert banned
artist entries or wiki pages to previous versions.
* The restrictions were inconsistent: in various places they were
either Member-only, Gold-only, or Builder-only.
* `legacy_normalize` came from c6012535, which is no longer a problem.
* `normalize_for_search` is only used for "[mass edit]" links
in artist entries. These links are a shortcut for performing a
`-artist_name source:<artist_url> -> artist_name` mass edit to tag
untagged artists, but this won't work for most sites these days.
