try using python 3.10

.github/workflows/formal-verifiation.yml

@@ -26,7 +26,7 @@ jobs:
       - uses: actions/checkout@v2
       - name: Install python
         uses: actions/setup-python@v2
-        with: { python-version: 3.6, cache: 'pip' }
+        with: { python-version: 3.10, cache: 'pip' }
       - name: Install java
         uses: actions/setup-java@v1
         with: { java-version: '11', java-package: jre }