Fix syntax for referencing POD_IP

Signed-off-by: wei-chenglai <qazwsx0939059006@gmail.com>

Author: seanlaii

docs/administrator/security/security-considerations.md

@@ -94,5 +94,5 @@ spec:
               fieldPath: status.podIP
         command:
         - /bin/karmada-controller-manager
-        - --metrics-bind-address=${POD_IP}:8080
+        - --metrics-bind-address=$(POD_IP):8080
 ```

i18n/zh/docusaurus-plugin-content-docs/current/administrator/security/security-considerations.md

@@ -94,5 +94,5 @@ spec:
               fieldPath: status.podIP
         command:
         - /bin/karmada-controller-manager
-        - --metrics-bind-address=${POD_IP}:8080
+        - --metrics-bind-address=$(POD_IP):8080
 ```