Update CI to test with python 3.9

aiida-vasp support python >=3.10 only

Author: zhubonan

.github/workflows/ci.yml

@@ -34,7 +34,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12']
+        python-version: ['3.10', '3.11', '3.12']
 
     services:
       rabbitmq:
@@ -70,7 +70,7 @@ jobs:
 
     strategy:
       matrix:
-        python-version: ['3.9']
+        python-version: ['3.10']
 
     steps:
     - uses: actions/checkout@v2