Upgrade pip before installing torch in scbutterfly

[rcannood]

Describe your changes

Both scButterfly components stopped building, which is the whole of the current CI failure on main -- every other component is green in both Build and Test.

The failing line is the torch install:

pip install --no-cache-dir torch==1.13.1 torchvision==0.14.1 --index-url https://download.pytorch.org/whl/cu117

Nothing about it changed; typing_extensions did. The chain:

1. --index-url replaces PyPI, so every transitive dependency has to come off the PyTorch index too.
2. torch 1.13.1 needs typing-extensions. The PyTorch index links back to the PyPI-hosted typing_extensions-4.15.0-py3-none-any.whl.
3. The pip shipped in python:3.9 predates PEP 503 name normalisation in that check, so it discards the wheel: has inconsistent Name: expected 'typing-extensions', but metadata has 'typing_extensions'.
4. It falls back to the sdist. typing_extensions 4.15 builds with flit_core<4,>=3.11, which is not on the PyTorch index, and the build-dependency install inherits the same --index-url. ERROR: No matching distribution found for flit_core<4,>=3.11.

So it is a stale-pip bug that a third-party release tripped, not a change on our side and not the base images -- these two components are the only ones still on python:3.9 rather than openproblems/base_pytorch_nvidia:1.

Upgrading pip first fixes it: modern pip accepts the wheel, never reaches the sdist, and never needs flit_core.

Verified locally: both images build, and viash test passes for scbutterfly_train and scbutterfly_predict.

Leaving the python:3.9 + torch 1.13.1 stack alone here. Moving scButterfly onto base_pytorch_nvidia:1 means Python 3.12, torch 2.11 and numpy 2, against a component currently pinned to numpy==1.23.5 / scanpy==1.9.3 / anndata==0.8.0 / episcanpy==0.3.2 -- worth doing, but not as the fix that unbreaks CI.

Checklist before requesting a review

• I have performed a self-review of my code

• Check the correct box. Does this PR contain:

  • Breaking changes
  • New functionality
  • Major changes
  • Minor changes
  • Bug fixes

• Proposed changes are described in the CHANGELOG.md

• CI Tests succeed and look good!