fix python version

Author: PhilipVinc

.github/workflows/aot.yml

@@ -16,7 +16,7 @@ jobs:
         os:
           - ubuntu-latest
         architecture: [x64]
-        python-version: ['3.x']
+        python-version: ['3.9']
         julia-version:
           - '1.6'
           - '1'