Keep method signature the same to remove STRICT warnings

Due to the difference in the method signature, when running with E_STRICT, we get the following error:

Declaration of Codeception\Util\Driver\PostgreSql::select() should be compatible with Codeception\Util\Driver\Db::select($column, $table, array $criteria)

This fixes that error. I have run all the tests (upon applying https://github.com/Codeception/Codeception/pull/499, https://github.com/Codeception/Codeception/pull/498 ) and they are passing with this change.