Change the variable name "adp" to "a"

Author: sarutak

sql/core/src/main/scala/org/apache/spark/sql/execution/ExplainUtils.scala

@@ -218,8 +218,8 @@ object ExplainUtils extends AdaptiveSparkPlanHelper {
       plan: => QueryPlan[_],
       subqueries: ArrayBuffer[(SparkPlan, Expression, BaseSubqueryExec)]): Unit = {
     plan.foreach {
-      case adp: AdaptiveSparkPlanExec =>
-        getSubqueries(adp.executedPlan, subqueries)
+      case a: AdaptiveSparkPlanExec =>
+        getSubqueries(a.executedPlan, subqueries)
       case p: SparkPlan =>
         p.expressions.foreach (_.collect {
           case e: PlanExpression[_] =>