ci: run unit tests only on Python 3.11

Author: tngraf

.github/workflows/unit-test.yml

@@ -15,7 +15,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.8]
+        python-version: [3.11]
 
     steps:
     - uses: actions/checkout@v3