[nancy][gres] Set max walltime to a week

data/grid5000/sites/nancy/clusters/gres/nodes/gres-1.json

@@ -256,7 +256,7 @@
   "supported_job_types": {
     "besteffort": true,
     "deploy": true,
-    "max_walltime": 0,
+    "max_walltime": 604800,
     "queues": [
       "admin",
       "production"