fix wrong miniconda version

Author: srmnitc

.github/workflows/testing.yml

@@ -18,7 +18,7 @@ jobs:
     steps:
     - uses: actions/checkout@v4
     - name: Setup Mambaforge
-      uses: conda-incubator/setup-miniconda@v4
+      uses: conda-incubator/setup-miniconda@v3
       with:
           python-version: ${{ matrix.python-version }}
           miniforge-version: latest