Update requirements.txt (#2021)

* Update requirements.txt

* Update ci-testing.yml

* Update hubconf.py

.github/workflows/ci-testing.yml

           python test.py --img 128 --batch 16 --weights weights/${{ matrix.model }}.pt --device $di
           python test.py --img 128 --batch 16 --weights runs/train/exp/weights/last.pt --device $di
 
+          python hubconf.py  # hub
           python models/yolo.py --cfg models/${{ matrix.model }}.yaml  # inspect
           python models/export.py --img 128 --batch 1 --weights weights/${{ matrix.model }}.pt  # export
         shell: bash

hubconf.py

 
     imgs = [Image.open(x) for x in Path('data/images').glob('*.jpg')]
     results = model(imgs)
-    results.show()
     results.print()
+    results.save()

requirements.txt

 numpy>=1.18.5
 opencv-python>=4.1.2
 Pillow
-PyYAML>=5.3
+PyYAML>=3.13
 scipy>=1.4.1
 tensorboard>=2.2
 torch>=1.7.0