[CORE][MINOR] Remove redundant set master in OutputCommitCoordinatorIntegrationSuite

## What changes were proposed in this pull request?
Remove redundant set master in OutputCommitCoordinatorIntegrationSuite, as we are already setting it in SparkContext below on line 43.

## How was this patch tested?
existing tests

Author: Sandeep Singh <sandeep@techaddict.me>

Closes #13168 from techaddict/minor-1.

core/src/test/scala/org/apache/spark/scheduler/OutputCommitCoordinatorIntegrationSuite.scala

@@ -37,7 +37,6 @@ class OutputCommitCoordinatorIntegrationSuite
   override def beforeAll(): Unit = {
     super.beforeAll()
     val conf = new SparkConf()
-      .set("master", "local[2,4]")
       .set("spark.hadoop.outputCommitCoordination.enabled", "true")
       .set("spark.hadoop.mapred.output.committer.class",
         classOf[ThrowExceptionOnFirstAttemptOutputCommitter].getCanonicalName)