docs: add prefer_name to ApisixClusterConfig/v2 spec (#2249)

* add prefer name to apisix cluster config spec

* correct attribute

Author: kayx23

docs/en/latest/references/apisix_cluster_config_v2.md

@@ -36,6 +36,7 @@ See the [definition](https://github.com/apache/apisix-ingress-controller/blob/ma
 | monitoring                        | object  | Monitoring configurations.                     |
 | monitoring.prometheus             | object  | Prometheus configurations.                     |
 | monitoring.prometheus.enable      | boolean | When set to `true`, enables Prometheus.        |
+| monitoring.prometheus.prefer_name | boolean | When set to `true`, prints Route/Service name instead of their ID in Prometheus metrics. |
 | monitoring.skywalking             | object  | Apache SkyWalking configurations.              |
 | monitoring.skywalking.enable      | boolean | When set to `true`, enables SkyWalking.        |
 | monitoring.skywalking.sampleRatio | number  | Sample ratio for spans. Should be in `[0, 1]`. |