Bump to latest supported python & torch in README.md

[nevillelyh]

Example in README failed to build because torch 1.8.1+cu111 doesn't exist any more?

 > [deps 5/5] RUN --mount=type=cache,target=/root/.cache/pip pip install -t /dep -r /tmp/requirements.txt:
0.494 Looking in links: https://download.pytorch.org/whl/torch_stable.html
4.031 ERROR: Could not find a version that satisfies the requirement torch==1.8.1+cu111 (from versions: 1.13.0, 1.13.0+cpu, 1.13.0+cu116, 1.13.0+cu117, 1.13.0+cu117.with.pypi.cudnn, 1.13.1, 1.13.1+cpu, 1.13.1+cu116, 1.13.1+cu117, 1.13.1+cu117.with.pypi.cudnn, 2.0.0, 2.0.0+cpu, 2.0.0+cpu.cxx11.abi, 2.0.0+cu117, 2.0.0+cu117.with.pypi.cudnn, 2.0.0+cu118, 2.0.1, 2.0.1+cpu, 2.0.1+cpu.cxx11.abi, 2.0.1+cu117, 2.0.1+cu117.with.pypi.cudnn, 2.0.1+cu118, 2.0.1+rocm5.3, 2.0.1+rocm5.4.2, 2.1.0, 2.1.0+cpu, 2.1.0+cpu.cxx11.abi, 2.1.0+cu118, 2.1.0+cu121, 2.1.0+cu121.with.pypi.cudnn, 2.1.0+rocm5.5, 2.1.0+rocm5.6, 2.1.1, 2.1.1+cpu, 2.1.1+cpu.cxx11.abi, 2.1.1+cu118, 2.1.1+cu121, 2.1.1+cu121.with.pypi.cudnn, 2.1.1+rocm5.5, 2.1.1+rocm5.6, 2.1.2, 2.1.2+cpu, 2.1.2+cpu.cxx11.abi, 2.1.2+cu118, 2.1.2+cu121, 2.1.2+cu121.with.pypi.cudnn, 2.1.2+rocm5.5, 2.1.2+rocm5.6, 2.2.0, 2.2.0+cpu, 2.2.0+cpu.cxx11.abi, 2.2.0+cu118, 2.2.0+cu121, 2.2.0+rocm5.6, 2.2.0+rocm5.7, 2.2.1, 2.2.1+cpu, 2.2.1+cpu.cxx11.abi, 2.2.1+cu118, 2.2.1+cu121, 2.2.1+rocm5.6, 2.2.1+rocm5.7, 2.2.2, 2.2.2+cpu, 2.2.2+cpu.cxx11.abi, 2.2.2+cu118, 2.2.2+cu121, 2.2.2+rocm5.6, 2.2.2+rocm5.7, 2.3.0, 2.3.0+cpu, 2.3.0+cpu.cxx11.abi, 2.3.0+cu118, 2.3.0+cu121, 2.3.0+rocm5.7, 2.3.0+rocm6.0)
4.031 ERROR: No matching distribution found for torch==1.8.1+cu111