Setup proper Python version in the main CI workflow

Author: DataTriny

.github/workflows/ci.yml

@@ -51,6 +51,11 @@ jobs:
           toolchain: stable
           components: clippy
 
+      - name: Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.9'
+
       - name: restore cache
         uses: Swatinem/rust-cache@v2