Simplify action

.github/workflows/main.yaml

@@ -1,5 +1,4 @@
 # main test workflow; ported from .travis.yaml
-
 name: main
 
 on:
@@ -24,29 +23,9 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
-    - name: Cache conda
-      uses: actions/cache@v4
-      env:
-        # Increase this value to reset cache.
-        CACHE_NUMBER: 0
-      with:
-        path: ~/conda_pkgs_dir
-        key:
-          ${{ runner.os }}-conda-${{ env.CACHE_NUMBER }}
-
-    - name: Setup Conda Environment
-      uses: conda-incubator/setup-miniconda@v3
-      with:
-        miniconda-version: latest
-        activate-environment: test
-        show-channel-urls: true
-        use-only-tar-bz2: true
     - name: Build
       run: |
-        conda create --yes -n test python=${{ matrix.python-version }} gcc_linux-64
-        conda activate test
-        conda install --yes numpy nose cython mpi4py openmpi
-        python setup.py install
+        python -m build
     - name: Unit tests
       run: |
         pip install runtests