Update sys.path.append(str(ROOT)) (#4852)

* Update `sys.path.append(str(ROOT))`

* Cleanup

export.py

@@ -32,7 +32,7 @@ import torch.nn as nn
 from torch.utils.mobile_optimizer import optimize_for_mobile
 
 FILE = Path(__file__).resolve()
-ROOT = FILE.parents[0]  # yolov5/ dir
+ROOT = FILE.parents[0]  # YOLOv5 root directory
 if str(ROOT) not in sys.path:
     sys.path.append(str(ROOT))  # add ROOT to PATH