[SPARK-3170][CORE]: Bug Fix in Storage UI

current compeleted stage only need to remove its own partitions that are no longer cached. Currently, "Storage" in Spark UI may lost some rdds which are cached actually.
There's a typo ("Comleted") and there's no need to make a Set then add to it. Just call Set(). You say the intent is to only remove infos that are not cached, but it already seems to do that. This prevents not-completed elements from being removed?