[HOTFIX] SPARK-1399: remove outdated comments

as the original PR was merged before this mistake is found....fix here,

Sorry about that @pwendell, @andrewor14, I will be more careful next time

Author: CodingCat <zhunansjtu@gmail.com>

Closes #474 from CodingCat/hotfix_1399 and squashes the following commits:

f3a8ba9 [CodingCat] move outdated comments

core/src/main/scala/org/apache/spark/ui/jobs/StageTable.scala

@@ -37,7 +37,6 @@ private[ui] class StageTableBase(
   protected def isFairScheduler = parent.isFairScheduler
 
   protected def columns: Seq[Node] = {
-    // create dummy element to wrap the columns
     <th>Stage Id</th> ++
     {if (isFairScheduler) {<th>Pool Name</th>} else Seq.empty} ++
     <th>Description</th>