[SPARK-21260][SQL][MINOR] Remove the unused OutputFakerExec

## What changes were proposed in this pull request?

OutputFakerExec was added long ago and is not used anywhere now so we should remove it.

## How was this patch tested?
N/A

Author: Xingbo Jiang <xingbo.jiang@databricks.com>

Closes #18473 from jiangxb1987/OutputFakerExec.

sql/core/src/main/scala/org/apache/spark/sql/execution/basicPhysicalOperators.scala

@@ -584,17 +584,6 @@ case class CoalesceExec(numPartitions: Int, child: SparkPlan) extends UnaryExecN
   }
 }
 
-/**
- * A plan node that does nothing but lie about the output of its child.  Used to spice a
- * (hopefully structurally equivalent) tree from a different optimization sequence into an already
- * resolved tree.
- */
-case class OutputFakerExec(output: Seq[Attribute], child: SparkPlan) extends SparkPlan {
-  def children: Seq[SparkPlan] = child :: Nil
-
-  protected override def doExecute(): RDD[InternalRow] = child.execute()
-}
-
 /**
  * Physical plan for a subquery.
  */