Fix typo in WebUI

Author: Jacek Laskowski <jacek.laskowski@deepsense.io>

Closes #9444 from jaceklaskowski/TImely-fix.

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

@@ -49,7 +49,7 @@ private[ui] class StagePage(parent: StagesTab) extends WebUIPage("stage") {
             ("shuffle-read-time-proportion", "Shuffle Read Time"),
             ("executor-runtime-proportion", "Executor Computing Time"),
             ("shuffle-write-time-proportion", "Shuffle Write Time"),
-            ("serialization-time-proportion", "Result Serialization TIme"),
+            ("serialization-time-proportion", "Result Serialization Time"),
             ("getting-result-time-proportion", "Getting Result Time"))
 
           legendPairs.zipWithIndex.map {