SPARK-20213: Remove SPARK-10548 repro test.

There is no longer a need for this test because the case it reproduces
is fixed in two ways. First, there is a fix for the original problem
where execution IDs leaked across threads. Second, nested execution IDs
no longer cause exceptions outside of tests because there is no reason
to fail at runtime just to keep the SQL tab clean.

This test was passing in Maven, but failing in SBT.

sql/core/src/test/scala/org/apache/spark/sql/execution/SQLExecutionSuite.scala

@@ -25,32 +25,6 @@ import org.apache.spark.sql.SparkSession
 
 class SQLExecutionSuite extends SparkFunSuite {
 
-  test("concurrent query execution (SPARK-10548)") {
-    // Try to reproduce the issue with the old SparkContext
-    val conf = new SparkConf()
-      .set("spark.testing", "1") // required to throw an error for concurrent withNewExecutionId
-      .setMaster("local[*]")
-      .setAppName("test")
-    val badSparkContext = new BadSparkContext(conf)
-    try {
-      testConcurrentQueryExecution(badSparkContext)
-      fail("unable to reproduce SPARK-10548")
-    } catch {
-      case e: IllegalArgumentException =>
-        assert(e.getMessage.contains(SQLExecution.EXECUTION_ID_KEY))
-    } finally {
-      badSparkContext.stop()
-    }
-
-    // Verify that the issue is fixed with the latest SparkContext
-    val goodSparkContext = new SparkContext(conf)
-    try {
-      testConcurrentQueryExecution(goodSparkContext)
-    } finally {
-      goodSparkContext.stop()
-    }
-  }
-
   test("concurrent query execution with fork-join pool (SPARK-13747)") {
     val spark = SparkSession.builder
       .config("spark.testing", "1") // required to throw an error for concurrent withNewExecutionId