Lower page size to 4MB in TestHive

Author: JoshRosen

sql/hive/src/main/scala/org/apache/spark/sql/hive/test/TestHive.scala

@@ -56,6 +56,7 @@ object TestHive
         .set("spark.sql.test", "")
         .set("spark.sql.hive.metastore.barrierPrefixes",
           "org.apache.spark.sql.hive.execution.PairSerDe")
+        .set("spark.buffer.pageSize", "4m")
         // SPARK-8910
         .set("spark.ui.enabled", "false")))