When adding support for a new PyTorch version, do the following:

• Update .github/workflows/testing.yml (exclude combinations if necessary)
• Add new PyTorch version in README.rst (possibly update cudatoolkit version)
• Add new PyTorch version in docs/user/installation.rst (possibly update cudatoolkit version)
• Remove old PyTorch version (we officially support the 4 latest minor versions)
• Check if the other PyTorch versions had patch releases, bump their versions if necessary
• Create a PR to run the CI matrix
• Fix issues if any

For new Python versions, proceed in the same way. Also update PYTHON_VERSION in scripts/deploy.sh.