ci: update micromamba setup and version

Author: JoLo90

.github/workflows/pytest.yml

@@ -40,7 +40,7 @@ jobs:
 
       - name: Install Conda environment with Micromamba
         if: matrix.environment-type == 'conda'
-        uses: mamba-org/setup-micromamba@v2
+        uses: mamba-org/setup-micromamba@v3
         with:
           environment-file: ${{ env.REQUIREMENTS }}
           cache-downloads: false
@@ -49,6 +49,7 @@ jobs:
             python=${{ matrix.python-version }}
           condarc: |
             channel-priority: flexible
+          micromamba-version: '2.6.0-0'
         env:
           # build requirement filename.  First replacement is for the python
           # version, second is to add "-min" if needed