Add missing arb.sql to postgres-make-concepts.sql

[marcofanti]

Summary

medication/arb.sql exists in the mimic-iv/concepts_postgres/medication/ directory but is not referenced in postgres-make-concepts.sql. As a result, mimiciv_derived.arb is never created when running the standard concepts build.

Fix

Add \i medication/arb.sql after \i medication/antibiotic.sql in the medication section of postgres-make-concepts.sql (one line, alphabetical order).

Steps to reproduce

Run postgres-make-concepts.sql and then:

SELECT COUNT(*) FROM information_schema.tables
WHERE table_schema = 'mimiciv_derived' AND table_name = 'arb';
-- returns 0