fix import order

Author: xwu0226

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala

@@ -18,7 +18,7 @@
 package org.apache.spark.sql.catalyst.optimizer
 
 import scala.collection.immutable.HashSet
-import org.apache.spark.sql.catalyst.analysis.{DistinctAggregationRewriter, CleanupAliases, EliminateSubQueries}
+import org.apache.spark.sql.catalyst.analysis.{CleanupAliases, DistinctAggregationRewriter, EliminateSubQueries}
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.expressions.aggregate._
 import org.apache.spark.sql.catalyst.plans.Inner