Update conda-incubator/setup-miniconda action to v3

v2 started breaking because mamba was no longer being installed. Instead
of debugging I'm upgrading to the latest release which includes the
libmamba solver, making plain conda as fast as mamba.

Author: mx-moth

.github/actions/environment/action.yaml

@@ -52,9 +52,8 @@ runs:
           hashFiles('continuous-integration/environment.yaml') }}
 
     - name: Install base Conda environment
-      uses: conda-incubator/setup-miniconda@v2
+      uses: conda-incubator/setup-miniconda@v3
       with:
-        mamba-version: "*"
         environment-file: continuous-integration/environment.yaml
         python-version: ${{ inputs.python-version }}
         channels: conda-forge