Fix compilation error due to buildScan() being final

[tedyu]

This PR fixes the following compilation error:

[error] /home/jenkins/workspace/Spark-Master-Maven-with-YARN/HADOOP_PROFILE/hadoop-2.4/label/centos/sql/hive/src/main/scala/org/apache/spark/sql/hive/orc/OrcRelation.scala:174: overriding method buildScan in class HadoopFsRelation of type (requiredColumns: Array[String], filters: Array[org.apache.spark.sql.sources.Filter], inputPaths: Array[String])org.apache.spark.rdd.RDD[org.apache.spark.sql.catalyst.expressions.Row];
[error] method buildScan cannot override final member
[error] override def buildScan(requiredColumns: Array[String],

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Merged build triggered.

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Test build #33023 has started for PR 6246 at commit e5e94e1.

[vanzin]

#6244 should have fixed this already.

[SparkQA]

Test build #33023 has finished for PR 6246 at commit e5e94e1.

• This patch fails Spark unit tests.
• This patch merges cleanly.
• This patch adds no public classes.

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