Fix duplicate Schema.Enums for Postges.

Fixes issue gnormal#115

database/drivers/postgres/parse.go

@@ -599,7 +599,6 @@ func queryEnums(log *log.Logger, db *sql.DB, schemas []string) (map[string][]*da
 	SELECT      n.nspname, t.typname as type
 	FROM        pg_type t
 	LEFT JOIN   pg_catalog.pg_namespace n ON n.oid = t.typnamespace
-	JOIN        pg_enum e ON t.oid = e.enumtypid
 	WHERE       (t.typrelid = 0 OR (SELECT c.relkind = 'c' FROM pg_catalog.pg_class c WHERE c.oid = t.typrelid))
 	AND     NOT EXISTS(SELECT 1 FROM pg_catalog.pg_type el WHERE el.oid = t.typelem AND el.typarray = t.oid)
 	AND     n.nspname IN (%s)`