[FLINK-36876] Add doc for new configuration

Author: chenyuzhi

docs/layouts/shortcodes/generated/kubernetes_operator_config_configuration.html

@@ -140,6 +140,12 @@
             <td>Duration</td>
             <td>The timeout for the observer to wait the flink rest client to return.</td>
         </tr>
+        <tr>
+            <td><h5>kubernetes.operator.flink.client.io.threads</h5></td>
+            <td style="word-wrap: break-word;">60</td>
+            <td>Integer</td>
+            <td>The maximum number of io threads used by the flink rest client.</td>
+        </tr>
         <tr>
             <td><h5>kubernetes.operator.health.canary.resource.timeout</h5></td>
             <td style="word-wrap: break-word;">1 min</td>

docs/layouts/shortcodes/generated/system_section.html

@@ -50,6 +50,12 @@
             <td>Duration</td>
             <td>The timeout for the observer to wait the flink rest client to return.</td>
         </tr>
+        <tr>
+            <td><h5>kubernetes.operator.flink.client.io.threads</h5></td>
+            <td style="word-wrap: break-word;">60</td>
+            <td>Integer</td>
+            <td>The maximum number of io threads used by the flink rest client.</td>
+        </tr>
         <tr>
             <td><h5>kubernetes.operator.leader-election.enabled</h5></td>
             <td style="word-wrap: break-word;">false</td>

flink-kubernetes-operator/src/main/java/org/apache/flink/kubernetes/operator/config/KubernetesOperatorConfigOptions.java

@@ -117,7 +117,7 @@ public static String operatorConfigKey(String key) {
 
     @Documentation.Section(SECTION_SYSTEM)
     public static final ConfigOption<Integer> OPERATOR_FLINK_CLIENT_IO_THREADS =
-            operatorConfig("kubernetes.operator.flink.client.io.threads")
+            operatorConfig("flink.client.io.threads")
                     .intType()
                     .defaultValue(60)
                     .withDescription(