fix: grant watch on promotionstrategies to dashboard service account

The dashboard uses a cache-based client that requires watch permission
to set up informers for PromotionStrategy resources.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>
Signed-off-by: Patrick Martin <patmarti@redhat.com>

Author: patjlm

chart/templates/extras/dashboard/rbac.yaml

@@ -25,6 +25,7 @@ rules:
     verbs:
       - get
       - list
+      - watch
 ---
 apiVersion: rbac.authorization.k8s.io/v1
 kind: ClusterRoleBinding