Use python 3.11

I switched to utilizing datetime.UTC when converting from epoch time to datetime
since the older way is now deprecated.

.github/workflows/unit-tests.yaml

@@ -14,7 +14,7 @@ jobs:
       - name: Set up python
         uses: actions/setup-python@v4
         with:
-          python-version: '3.10'
+          python-version: '3.11'
 
       - name: Install dependencies
         run: |