[doc]Fix autograd.detect_anomaly docs incorrectly formatted (#51335)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/51141
Two bullet points don't render as bullet points.
Before
<img width="657" alt="screenshot before" src="https://user-images.githubusercontent.com/19372617/106240701-125a3080-6248-11eb-9572-f915aa9b72e1.png">
After
<img width="888" alt="screenshot after" src="https://user-images.githubusercontent.com/19372617/106240714-17b77b00-6248-11eb-8e54-51be103639e9.png">
Pull Request resolved: https://github.com/pytorch/pytorch/pull/51335
Reviewed By: izdeby
Differential Revision: D26148582
Pulled By: ezyang
fbshipit-source-id: 5aff6f9bd7affdf13bec965e9bf1a417e5caa88d
