add comment on python versions

.gitlab-ci.yml

@@ -18,10 +18,9 @@ test-python:
   parallel:
     matrix:
       - PYTHON_VERSION: [
-#          '3.7',
-          '3.8',
-#          '3.9',
-          '3.10',
+#          '3.7', # EOL
+          '3.8', # oldest
+          '3.10', # used in Dockerfile
           '3.12', # latest
       ]