CI: update Python version matrix

Old Python versions do not support the modern type annotation
syntax. It's time to update the test matrix.

We'll include 3.12 in a separate PR, need to fix some tests first.

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: