multipy/compat-requirements: add functorch (#147)

Summary:
functorch was added as a hard dep to dynamo: pytorch/torchdynamo@2b6db3b

Fixes:
https://github.com/pytorch/multipy/runs/8076965287?check_suite_focus=true

Pull Request resolved: #147

Reviewed By: voznesenskym

Differential Revision: D39147670

Pulled By: d4l3k

fbshipit-source-id: a6be1f7f5400c19c6f286b54b743b42cd3e9329d

Author: d4l3k

compat-requirements.txt

@@ -3,3 +3,4 @@ torchaudio
 torchvision
 git+https://github.com/facebookresearch/pytorch3d.git
 git+https://github.com/pytorch/torchdynamo.git
+git+https://github.com/pytorch/pytorch.git#subdirectory=functorch