Follow-up to d0453881: the pgUserReputationsTable definition and the
UserReputation/UserReputationInsert type aliases were the only remaining
references to the removed user reputation feature. Nothing imports them
(verified via grep across src/ + tests/), so they're pure dead code that
could mislead future devs into re-joining a dropped table. Railed out to
close the 42P01 failure class completely.