[SPARK-20548] Disable ReplSuite.newProductSeqEncoder with REPL defined class

## What changes were proposed in this pull request?

`newProductSeqEncoder with REPL defined class` in `ReplSuite` has been failing in-deterministically : https://spark-tests.appspot.com/failed-tests over the last few days. Disabling the test until a fix is in place.

https://spark.test.databricks.com/job/spark-master-test-sbt-hadoop-2.7/176/testReport/junit/org.apache.spark.repl/ReplSuite/newProductSeqEncoder_with_REPL_defined_class/history/

## How was this patch tested?

N/A

Author: Sameer Agarwal <sameerag@cs.berkeley.edu>

Closes #17823 from sameeragarwal/disable-test.

repl/scala-2.11/src/test/scala/org/apache/spark/repl/ReplSuite.scala

@@ -474,7 +474,8 @@ class ReplSuite extends SparkFunSuite {
     assertDoesNotContain("Exception", output)
   }
 
-  test("newProductSeqEncoder with REPL defined class") {
+  // TODO: [SPARK-20548] Fix and re-enable
+  ignore("newProductSeqEncoder with REPL defined class") {
     val output = runInterpreterInPasteMode("local-cluster[1,4,4096]",
       """
       |case class Click(id: Int)