Update requirements.txt to coremltools==4.0b3

fb05681a · Glenn Jocher · d0f98c00 · fb05681a
--- a/requirements.txt
+++ b/requirements.txt
@@ -17,8 +17,9 @@ tqdm>=4.41.0
 # pycocotools>=2.0
 # export --------------------------------------
-# coremltools==4.0b2
+# coremltools==4.0b3
 # onnx>=1.7.0
+# packaging  # for coremltools
 # extras --------------------------------------
 # thop