Drop Python 3.8 and 3.9 tests

Python 3.9 does not support modern type hints. It's no longer
supported by coriolis-core, as such we'll drop it from the
python-coriolisclient pipeline.

Author: petrutlucian94

.github/workflows/unit-tests.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-22.04
     strategy:
       matrix:
-        python-version: ["3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.10", "3.11"]
         architecture: ["x64"]
 
     steps: