Use Mambaforge for github action

miniconda is broken on python 3.11 + macOS

Author: timj

.github/workflows/build.yaml

@@ -20,14 +20,16 @@ jobs:
       - uses: conda-incubator/setup-miniconda@v2
         with:
           python-version: ${{ matrix.pyversion }}
+          auto-update-conda: true
           channels: conda-forge,defaults
+          miniforge-variant: Mambaforge
+          use-mamba: true
           channel-priority: strict
           show-channel-urls: true
 
       - name: Install conda packages used by this package
         shell: bash -l {0}
         run: |
-          conda install mamba
           mamba install -y -q scons eups compilers ruff flake8
 
       # We have two cores so we can speed up the testing with xdist
@@ -40,7 +42,7 @@ jobs:
       - name: List installed packages
         shell: bash -l {0}
         run: |
-          conda list
+          mamba list
           pip list -v
 
       - name: Build and test