fix doc build

Summary: follow up of D31575602 (0e29b7a)

Differential Revision: D31733407

fbshipit-source-id: f367fbcfd6764278bc263982159dac531e15c670

Author: ppwwyyxx

docs/requirements.txt

@@ -15,7 +15,7 @@ cloudpickle
 Pillow
 future
 git+git://github.com/facebookresearch/fvcore.git
-https://download.pytorch.org/whl/cpu/torch-1.7.0%2Bcpu-cp37-cp37m-linux_x86_64.whl
-https://download.pytorch.org/whl/cpu/torchvision-0.8.1%2Bcpu-cp37-cp37m-linux_x86_64.whl
+https://download.pytorch.org/whl/cpu/torch-1.8.0%2Bcpu-cp37-cp37m-linux_x86_64.whl
+https://download.pytorch.org/whl/cpu/torchvision-0.9.1%2Bcpu-cp37-cp37m-linux_x86_64.whl
 omegaconf>=2.1.0.dev24
 hydra-core>=1.1.0.dev5