Update tests.yml

Author: albangaignard

.github/workflows/tests.yml

@@ -16,16 +16,16 @@ jobs:
 
     steps:
       - uses: actions/checkout@v2
-      - name: Set up Python 3.8
+      - name: Set up Python 3.9
         uses: actions/setup-python@v2
         with:
-          python-version: 3.8
+          python-version: 3.9
       #----------------------------------------------
       #  -----  install & configure conda
       #----------------------------------------------
       - uses: conda-incubator/setup-miniconda@v2
         with:
-          python-version: 3.8
+          python-version: 3.9
           conda-build-version: "*"
           channels: conda-forge,defaults
           channel-priority: true