Fix unknown attribute reference error

Author: MarkSiemers-msr

lib/job-iteration/active_record_batch_enumerator.rb

@@ -29,7 +29,7 @@ def initialize(relation, columns: nil, batch_size: 100, cursor: nil)
         raise JobIteration::ActiveRecordCursor::ConditionNotSupportedError
       end
 
-      @base_relation = relation.reorder(@columns.join(","))
+      @base_relation = relation.reorder(*@columns)
     end
 
     def each