Revert "CircleCI: fix NCCL install (#14124)" (#14146)

Revert "CircleCI: fix NCCL install (#14124)" (#14146)

Summary:
This reverts commit a1fa9d8cf9b2b0e7373ec420c2487d4dfd0e587c.

[pytorch_linux_trusty_py2_7_9_build](https://circleci.com/gh/pytorch/pytorch/270206?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link/console):
```
Nov 17 07:37:27 + sudo apt-get -qq update
Nov 17 07:37:30 W: Ignoring Provides line with DepCompareOp for package gdb-minimal
Nov 17 07:37:30 W: You may want to run apt-get update to correct these problems
Nov 17 07:37:30 + sudo apt-get -qq install --allow-downgrades --allow-change-held-packages openmpi-bin libopenmpi-dev
Nov 17 07:37:30 E: Command line option --allow-downgrades is not understood
Nov 17 07:37:30 + cleanup
Nov 17 07:37:30 + retcode=100
Nov 17 07:37:30 + set +x
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/14146

Differential Revision: D13113912

Pulled By: bddppq

fbshipit-source-id: cd9d371cf72159f03d12a8b56ed5bd2060ebbe59