CI: stop testing against ancient GAP versions

Author: fingolfin

.github/workflows/CI.yml

@@ -30,9 +30,6 @@ jobs:
           - stable-4.14
           - stable-4.13
           - stable-4.12
-          - stable-4.11
-          - stable-4.10
-          - stable-4.9
 
     steps:
       - uses: actions/checkout@v5