Bump scipy>=1.5 to meet numpy constraints (#7646)

Resolves https://github.com/ultralytics/yolov5/issues/7638

requirements.txt

@@ -7,7 +7,7 @@ opencv-python>=4.1.1
 Pillow>=7.1.2
 PyYAML>=5.3.1
 requests>=2.23.0
-scipy>=1.4.1
+scipy>=1.5
 torch>=1.7.0
 torchvision>=0.8.1
 tqdm>=4.41.0