bump RL9 fatimage

https://github.com/stackhpc/ansible-slurm-appliance/actions/runs/20331802030/job/58408928975

Author: elelaysh

environments/.stackhpc/tofu/cluster_image.auto.tfvars.json

@@ -1,6 +1,6 @@
 {
   "cluster_image": {
     "RL8": "openhpc-RL8-251215-1349-ae20d969",
-    "RL9": "openhpc-RL9-251215-1348-ae20d969"
+    "RL9": "openhpc-RL9-251218-0916-ca120f3d"
   }
 }