test: switch back to gams:latest to check GAMS 53 compatibility

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: mbaronnet

.github/workflows/gams_workflow.yml

@@ -10,7 +10,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     container:
-      image: gams/gams:48
+      image: gams/gams:latest
 
     steps:
       - name: Check out repository