simplify ci test action

Author: jcmgray

.github/workflows/tests.yml

@@ -82,10 +82,7 @@ jobs:
       with:
         python-version: ${{ matrix.python-version }}
         miniforge-version: latest
-        activate-environment: test-env
         environment-file: ci/requirements/py-${{ matrix.conda-env }}.yml
-        channels: conda-forge
-        conda-remove-defaults: "true"
 
     - name: Matrix submodule tests with pytest
       if: ${{ matrix.testset == 'matrix' }}