Use the conda channel defined in docker.Makefile to install cudatoolkit (#53316)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/53316
Test Plan:
Nightly Docker build CI
This is a follow-up PR after docker moved default CUDA => 11.1. Only merge this after https://github.com/pytorch/pytorch/issues/53299 is committed.
Reviewed By: albanD
Differential Revision: D26996287
Pulled By: xuzhao9
fbshipit-source-id: 0c2e03da41d036d7aada3e07d479a3dede219f58
