HBASE-24088 Solve the ambiguous reference for scala 2.12 (#63)

Signed-off-by: Balazs Meszaros <meszibalu@apache.org>
diff --git a/spark/hbase-spark/src/main/scala/org/apache/hadoop/hbase/spark/datasources/HBaseTableScanRDD.scala b/spark/hbase-spark/src/main/scala/org/apache/hadoop/hbase/spark/datasources/HBaseTableScanRDD.scala
index 6c06811..346983c 100644
--- a/spark/hbase-spark/src/main/scala/org/apache/hadoop/hbase/spark/datasources/HBaseTableScanRDD.scala
+++ b/spark/hbase-spark/src/main/scala/org/apache/hadoop/hbase/spark/datasources/HBaseTableScanRDD.scala
@@ -213,7 +213,7 @@
     val scans = partition.scanRanges
       .map(buildScan(_, filter, columns))
     val tableResource = TableResource(relation)
-    context.addTaskCompletionListener(context => close())
+    context.addTaskCompletionListener[Unit](context => close())
     val points = partition.points
     val gIt: Iterator[Result] =  {
       if (points.isEmpty) {