* remove unused functionality
We can now safely delete all the logic around users who are on trial and
signed up *before* the business tiers release, since that's no longer
possible
* add monthly_pageview_limit fn clause that takes a user
* make Quota.site_limit return enterprise site limit
...not `:unlimited`, as we still need to display it
in the account settings.
* make `team_member_limit/1` return :unlimited on small_build
* improve team_member_usage/1 function doc
* stop displaying unlimited symbol in usage section
These unlimited limits include:
* `monthly_pageview_limit` for trials
* `team_member_limit` for old enterprise plans
* `site limit` for old accounts (before 2021-05-05)
* format
* small refactor case clause + move mod vars
* review suggestions