Fix typo (#3039)

momet -> moment
Signed-off-by: Hollow Man <hollowman@hollowman.ml>
Co-authored-by: Vasilis Vryniotis <datumbox@users.noreply.github.com>

docs/source/io.rst

@@ -35,7 +35,7 @@ Example of inspecting a video:
     import torchvision
     video_path = "path to a test video"
     # Constructor allocates memory and a threaded decoder
-    # instance per video. At the momet it takes two arguments:
+    # instance per video. At the moment it takes two arguments:
     # path to the video file, and a wanted stream.
     reader = torchvision.io.VideoReader(video_path, "video")