Fix masks shape comment for display_instances

visualize.py

@@ -78,7 +78,7 @@ def display_instances(image, boxes, masks, class_ids, class_names,
                       figsize=(16, 16), ax=None):
     """
     boxes: [num_instance, (y1, x1, y2, x2, class_id)] in image coordinates.
-    masks: [num_instances, height, width]
+    masks: [height, width, num_instances]
     class_ids: [num_instances]
     class_names: list of class names of the dataset
     scores: (optional) confidence scores for each box