[Installation] conda installation hangs on "Solving environment"
Labels: oncall: binaries, triaged

### 🐛 Describe the bug

Hi,

I was trying to install pytorch following the main instruction on the website.

Setup is:
- PyTorch (Stable) 1.12.1
- Linux Ubuntu 20.04
- Conda package
- Language Python
- CUDA 11.6

I was able to install for CUDA 10.2, but I discover I have the 11.6 installed. 

With the command given:
```bash
conda install pytorch torchvision torchaudio cudatoolkit=11.6 -c pytorch -c conda-forge
```
The installation hangs on:
```bash
Collecting package metadata (current_repodata.json): done
Solving environment: failed with initial frozen solve. Retrying with flexible solve.
Collecting package metadata (repodata.json): done
Solving environment: / 
```

I solved not installing `cudatoolkit` first:
```
conda install pytorch torchvision torchaudio -c pytorch -c conda-forge
```
but this install the `cudatoolkit-10.2.89`

Hence I installed the right `cudatoolkit` version:
```
conda install -c pytorch -c conda-forge cudatoolkit=11.6
```
The output of this is:
```
The following packages will be UPDATED:

  cudatoolkit                            10.2.89-h8f6ccaa_8 --> 11.6.0-hecad31d_10
  libgcc-ng                               9.3.0-h5101ec6_17 --> 11.2.0-h1234567_1
  libgomp                                 9.3.0-h5101ec6_17 --> 11.2.0-h1234567_1
  libstdcxx-ng       pkgs/main::libstdcxx-ng-9.3.0-hd4cf53~ --> conda-forge::libstdcxx-ng-12.1.0-ha89aaad_16

The following packages will be SUPERSEDED by a higher-priority channel:

  openssl              pkgs/main::openssl-1.1.1q-h7f8727e_0 --> conda-forge::openssl-1.1.1o-h166bdaf_0

The following packages will be DOWNGRADED:

  pytorch                1.12.1-py3.8_cuda10.2_cudnn7.6.5_0 --> 1.12.1-py3.8_cuda11.6_cudnn8.3.2_0
  torchaudio                              0.12.1-py38_cu102 --> 0.12.1-py38_cu116
  torchvision                             0.13.1-py38_cu102 --> 0.13.1-py38_cu116
```

I find it strange that `pytorch` `torchaudio` `torchvision` are considered "DOWNGRADED"

BTW following the steps above it seems I solved the installation issue


### Versions
```
Collecting environment information...
PyTorch version: 1.12.1
Is debug build: False
CUDA used to build PyTorch: 11.6
ROCM used to build PyTorch: N/A

OS: Ubuntu 20.04.4 LTS (x86_64)
GCC version: (Ubuntu 9.4.0-1ubuntu1~20.04.1) 9.4.0
Clang version: Could not collect
CMake version: version 3.16.3
Libc version: glibc-2.31

Python version: 3.8.13 (default, Mar 28 2022, 11:38:47)  [GCC 7.5.0] (64-bit runtime)
Python platform: Linux-5.15.0-46-generic-x86_64-with-glibc2.17
Is CUDA available: True
CUDA runtime version: Could not collect
GPU models and configuration: GPU 0: NVIDIA GeForce GTX 1650
Nvidia driver version: 510.85.02
cuDNN version: Could not collect
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

Versions of relevant libraries:
[pip3] numpy==1.21.5
[pip3] torch==1.12.1
[pip3] torchaudio==0.12.1
[pip3] torchvision==0.13.1
[conda] blas                      1.0                         mkl  
[conda] cudatoolkit               11.6.0              hecad31d_10    conda-forge
[conda] ffmpeg                    4.3                  hf484d3e_0    pytorch
[conda] mkl                       2021.4.0           h06a4308_640  
[conda] mkl-service               2.4.0            py38h497a2fe_0    conda-forge
[conda] mkl_fft                   1.3.1            py38hd3c417c_0  
[conda] mkl_random                1.2.2            py38h1abd341_0    conda-forge
[conda] numpy                     1.21.5           py38he7a7128_2  
[conda] numpy-base                1.21.5           py38hf524024_2  
[conda] pytorch                   1.12.1          py3.8_cuda11.6_cudnn8.3.2_0    pytorch
[conda] pytorch-mutex             1.0                        cuda    pytorch
[conda] torchaudio                0.12.1               py38_cu116    pytorch
[conda] torchvision               0.13.1               py38_cu116    pytorch
```


cc @ezyang @seemethere @malfet