Use Python 3.9 on the CI

Author: arteymix

.github/workflows/build.yml

@@ -13,7 +13,7 @@ jobs:
     - name: Set up Python 3.10
       uses: actions/setup-python@v5
       with:
-        python-version: '3.10'
+        python-version: '3.9'
     - name: Add conda to system path
       run: |
         # $CONDA is an environment variable pointing to the root of the miniconda directory