Update Mambaforge to Miniforge3 in test GHA (#302)

* remove defaults channel

* Miniforge3

Author: HGWright

.github/workflows/ci-tests.yml

@@ -59,9 +59,9 @@ jobs:
     - name: "mambaforge setup (python ${{ matrix.python-version }})"
       uses: conda-incubator/setup-miniconda@v3
       with:
-        miniforge-variant: Mambaforge
+        miniforge-variant: Miniforge3
         miniforge-version: latest
-        channels: conda-forge,defaults
+        channels: conda-forge
         channel-priority: true
         auto-update-conda: true
         environment-file: "requirements/locks/py${{ matrix.python-version }}-linux-64.lock"