Update base for Update on "[doc] fix amp doc"

# Motivation
The doc shown on https://pytorch.org/docs/main/amp.html#torch.amp.autocast_mode.is_autocast_available should be `torch.amp.is_autocast_available` instead of `torch.amp.autocast_mode.is_autocast_available`. This PR aims to fix it.



cc mcarilli ptrblck leslie-fang-intel jgong5

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