FIX(alertmanager): remove duplicate volume config

- Remove extraVolumes and extraVolumeMounts
- Chart uses emptyDir automatically when persistence disabled

alertmanager/helm-values.yaml

@@ -17,18 +17,10 @@ affinity:
           topologyKey: kubernetes.io/hostname
 
 # Use emptyDir instead of PVC (alert state is temporary)
+# Chart automatically uses emptyDir when persistence is disabled
 persistence:
   enabled: false
 
-extraVolumes:
-  - name: storage
-    emptyDir:
-      sizeLimit: 500Mi
-
-extraVolumeMounts:
-  - name: storage
-    mountPath: /alertmanager
-
 resources:
   requests:
     cpu: 15m