change tests to run on python 3.9 (#776)

Author: haritamar

.github/workflows/test-warehouse.yml

@@ -84,7 +84,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: "3.8"
+          python-version: "3.9"
           cache: "pip"
 
       - name: Install Spark requirements