Revert unneeded changes

Author: MaxGekk

sql/core/src/test/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetPartitionDiscoverySuite.scala

@@ -36,6 +36,7 @@ import org.apache.spark.sql.catalyst.util.DateTimeUtils
 import org.apache.spark.sql.execution.datasources._
 import org.apache.spark.sql.execution.datasources.{PartitionPath => Partition}
 import org.apache.spark.sql.execution.streaming.MemoryStream
+import org.apache.spark.sql.functions._
 import org.apache.spark.sql.internal.SQLConf
 import org.apache.spark.sql.test.SharedSQLContext
 import org.apache.spark.sql.types._