Remove all conda 3.5 nightly configs, remove libtorch smoketests (#21380)
Summary:
| | Before | After
------------ | ------------ | -------------
Binary builds |  |  |
Smoke tests |  |  |
Pull Request resolved: https://github.com/pytorch/pytorch/pull/21380
Differential Revision: D15634729
Pulled By: kostmo
fbshipit-source-id: aef44b0e5b9997be55d93969ab85effca68c5c88
