[skip ci] Add comment for taskScheduler start (#9755)

Signed-off-by: Nxige-16 <xi.ge@zilliz.com>

internal/querycoord/task_scheduler.go

@@ -814,6 +814,7 @@ func (scheduler *TaskScheduler) processActivateTaskLoop() {
 	}
 }
 
+// Start function start two goroutines to process trigger tasks and internal tasks
 func (scheduler *TaskScheduler) Start() error {
 	scheduler.wg.Add(2)
 	go scheduler.scheduleLoop()