Fix/ci torch cpu

[nceglia]

Fix the CI workflow on branch fix/ci-torch-cpu. In .github/workflows/tests.yml, replace the Install dependencies step with:

  - name: Install dependencies
    run: |
      pip install maturin
      maturin build --release
      pip install target/wheels/*.whl
      pip install torch --index-url https://download.pytorch.org/whl/cpu
      pip install pytest numpy scipy scikit-learn scanpy anndata tqdm seaborn matplotlib pandas leidenalg umap-learn scikit-misc

Make the same change in .github/workflows/release.yml in the test job.