The drop_sql loop covered relations, routines, sequences and types but
not pg_collation, so a dump's CREATE COLLATION (OpenProject's ICU
public.versions_name) aborted the ON_ERROR_STOP replay with 'collation
already exists'. Add the fifth UNION ALL branch; DROP COLLATION IF
EXISTS public.<name> CASCADE rides the existing loop, and the loop
already drops every user table, so CASCADE fallout is absorbed by the
IF EXISTS no-ops.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
