upgrading PL via pip uninstalls pytorch-1.8
🐛 Bug
To Reproduce

$ pip install pytorch-lightning -U
[...]
Installing collected packages: torch, pytorch-lightning
  Attempting uninstall: torch
    Found existing installation: torch 1.8.0.dev20201106+cu110
    Uninstalling torch-1.8.0.dev20201106+cu110:
      Successfully uninstalled torch-1.8.0.dev20201106+cu110

Expected behavior
It shouldn't uninstall pytorch-1.8.
Nvidia RTX-30* don't work with pytorch < 1.8.
Environment
* CUDA:
        - GPU:
                - GeForce RTX 3090
                - GeForce GTX 1070 Ti
        - available:         True
        - version:           10.2
* Packages:
        - numpy:             1.19.4
        - pyTorch_debug:     True
        - pyTorch_version:   1.7.0
        - pytorch-lightning: 1.0.5
        - tqdm:              4.50.2
* System:
        - OS:                Linux
        - architecture:
                - 64bit
                - ELF
        - processor:         x86_64
        - python:            3.8.5
        - version:           #57-Ubuntu SMP Thu Oct 15 10:57:00 UTC 2020

Additional context