remove micromamba pin

Author: jorisvandenbossche

.github/actions/setup-conda/action.yml

@@ -9,8 +9,6 @@ runs:
     - name: Install ${{ inputs.environment-file }}
       uses: mamba-org/setup-micromamba@v1
       with:
-        # Pinning to avoid 2.0 failures
-        micromamba-version: '1.5.10-0'
         environment-file: ${{ inputs.environment-file }}
         environment-name: test
         condarc-file: ci/.condarc