[SequenceManager] Fix outdated comment

Leftover comment fix from my foray into this code.

Code to be ripped out soon by shaseley@ (removing anti-starvation logic)
but might as well have a correct comment in the mean time.

R=alexclarke@chromium.org

Bug: 1031336
Change-Id: Ibbe1814144444dff23242dbbdf127b4fb0d9fb50
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1958585
Auto-Submit: Gabriel Charette <gab@chromium.org>
Commit-Queue: Alex Clarke <alexclarke@chromium.org>
Reviewed-by: Alex Clarke <alexclarke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#723295}

base/task/sequence_manager/task_queue_selector.cc

@@ -210,8 +210,8 @@ WorkQueue* TaskQueueSelector::SelectWorkQueueToService() {
                              ChooseWithPriority<SetOperationOldest>(
                                  priority, &chose_delayed_over_immediate);
 
-  // If we still have any tasks remaining for |set_index| then adjust it's
-  // sort key.
+  // If we still have any tasks remaining for |priority| then adjust its sort
+  // key.
   if (active_priorities_.IsInQueue(priority))
     active_priorities_.ChangeMinKey(GetSortKeyForPriority(priority));