Removed an unused import

Author: liancheng

sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala

@@ -32,7 +32,7 @@ import org.apache.spark.sql.catalyst.types._
 import org.apache.spark.sql.catalyst.optimizer.Optimizer
 import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
 import org.apache.spark.sql.catalyst.rules.RuleExecutor
-import org.apache.spark.sql.columnar.{InMemoryColumnarTableScan, InMemoryRelation}
+import org.apache.spark.sql.columnar.InMemoryRelation
 import org.apache.spark.sql.execution._
 import org.apache.spark.sql.execution.SparkStrategies
 import org.apache.spark.sql.json._