[anaconda] Remove Anaconda option from pytorch getting started page matrix

[atalman]

Related to pytorch/pytorch#138506

We would like to remove conda option from the quick start module of getting started page here:

Please make sure the code that generates the automatic update PR still works: https://github.com/pytorch/pytorch.github.io/blob/site/.github/workflows/update-quick-start-module.yml

Hence after this update we should run the workflow above and make sure it completes without error.

[Camyll]

@atalman do you think we should remove all references to conda installation in the entire page? Or do we have another task for this? Thanks!