Reduce aio flavor to en1.medium

This flavor has 8G memory and is cheaper than en1.large.

Author: markgoddard

.github/workflows/stackhpc-all-in-one.yml

@@ -38,7 +38,7 @@ on:
       vm_flavor:
         description: Flavor for the all-in-one VM
         type: string
-        default: en1.large
+        default: en1.medium
       vm_network:
         description: Network for the all-in-one VM
         type: string