While the case tested (`lain@ple`) gives wrong ordering due to
using only trigram to order, it almost never happens in reality. In reality
it would be either `lain` (in which case it's fine to list the user with `lain`
in display name first), or `@lain@pleroma.soykaf.com`/`lain@pleroma.soykaf.com` (which is
handled fine as well)
- Remove trigram as it tends to rank garbage results highly, resulting
in it prioritized above fts, which gives actually decent results. ACKed
by kaniini and lain on irc.
- Remove a test for handling misspelled requests, since we no longer have
trigram
- Remove a test for searching users with `nil` display names, because it
is unrealistic, we don't accept usernames that are not >1 char strings
- Make rank boosting for followers/followees sane again, previous values
resulted in garbage matches getting on top just because the users are
followers/followees
