Update README.md (#4387)

README.md

@@ -112,7 +112,7 @@ $ python detect.py --source 0  # webcam
                             file.mp4  # video
                             path/  # directory
                             path/*.jpg  # glob
-                            'https://youtu.be/NUsoVlDFqZg'  # YouTube video
+                            'https://youtu.be/NUsoVlDFqZg'  # YouTube
                             'rtsp://example.com/media.mp4'  # RTSP, RTMP, HTTP stream
 ```