Fix test/csv-guess.load for old PostgreSQL.

In travis environment we still test with PostgreSQL 9.1 and 9.6, and there's
no reason for this test to use a modern spelling of create schema, after
all.

It works because the test/csv-before-after.load creates the schema and is
ran before test/csv-guess.load. That's good enough for now.

test/csv-guess.load

@@ -6,7 +6,6 @@ LOAD CSV
      WITH truncate
 
    BEFORE LOAD DO
-    $$ create schema if not exists csv; $$,
     $$ drop table if exists csv.track; $$,
     $$ create table csv.track (
           trackid      bigserial primary key,