chore(ci): Fix miniforge installation

Author: effigies

.github/workflows/pythonpackage.yml

@@ -68,8 +68,10 @@ jobs:
         uses: conda-incubator/setup-miniconda@v3
         with:
           python-version: ${{ matrix.python-version }}
-          mamba-version: "*"
-          channels: ${{ env.FSLCONDA }},conda-forge,defaults
+          # mamba env config does not work in 2.*
+          # Track: https://github.com/mamba-org/mamba/issues/1881
+          mamba-version: "1.*"
+          channels: ${{ env.FSLCONDA }},conda-forge
           channel-priority: true
       - name: Install FSL
         run: |