Calico: 3.20.0 policy update to allow access to endpointslices (#7899)

roles/network_plugin/calico/templates/calico-cr.yml.j2

@@ -13,6 +13,16 @@ rules:
       - configmaps
     verbs:
       - get
+{% if calico_version is version("v3.20.0", ">=") %}
+  # EndpointSlices are used for Service-based network policy rule
+  # enforcement.
+  - apiGroups: ["discovery.k8s.io"]
+    resources:
+      - endpointslices
+    verbs:
+      - watch
+      - list
+{% endif %}
   - apiGroups: [""]
     resources:
       - endpoints