[skip ci] Add comment for removePartitionFlowGraph (#12027)

Signed-off-by: Nbigsheeper <yihao.dai@zilliz.com>

internal/querynode/data_sync_service.go

@@ -263,6 +263,7 @@ func (dsService *dataSyncService) startPartitionFlowGraph(partitionID UniqueID,
 	return nil
 }
 
+// removePartitionFlowGraph removes the partition flow graph from dataSyncService by partitionID
 func (dsService *dataSyncService) removePartitionFlowGraph(partitionID UniqueID) {
 	dsService.mu.Lock()
 	defer dsService.mu.Unlock()