The maxNumPostShufflePartitions config should obey reducePostShufflePartitions enabled

The config "spark.sql.adaptive.shuffle.maxNumPostShufflePartitions" should be controlled by not only "spark.sql.adaptive.enabled", but also "spark.sql.adaptive.shuffle.reducePostShufflePartitions.enabled", that keeps the same behavior of minNumPostShufflePartitions and targetPostShuffleInputSize.