activity: when restricting deactivated users, precalculate the user list
the PostgreSQL query planner is easily confused due to the complexity of
certain queries we make. while we plan to simplify these queries through
unification of activities and objects, we are not yet there. it has been
discovered that using a precalculated list of deactivated users encourages
the query planner to prefer simpler indices instead of the
activity_visibility index.
accordingly, drop the subquery and precalc the user list instead.
projects / akkoma / commit