[FLINK-23845][docs] Improve PushGatewayReporter config:deleteOnShutdown description

This closes apache#16823.

Author: camilesing

docs/layouts/shortcodes/generated/prometheus_push_gateway_reporter_configuration.html

@@ -12,7 +12,7 @@
             <td><h5>deleteOnShutdown</h5></td>
             <td style="word-wrap: break-word;">true</td>
             <td>Boolean</td>
-            <td>Specifies whether to delete metrics from the PushGateway on shutdown.</td>
+            <td>Specifies whether to delete metrics from the PushGateway on shutdown. Flink will try its best to delete the metrics but this is not guaranteed. See <a href="https://issues.apache.org/jira/browse/FLINK-13787">here</a> for more details.</td>
         </tr>
         <tr>
             <td><h5>filterLabelValueCharacters</h5></td>

flink-metrics/flink-metrics-prometheus/src/main/java/org/apache/flink/metrics/prometheus/PrometheusPushGatewayReporterOptions.java

@@ -54,7 +54,14 @@ public class PrometheusPushGatewayReporterOptions {
             ConfigOptions.key("deleteOnShutdown")
                     .defaultValue(true)
                     .withDescription(
-                            "Specifies whether to delete metrics from the PushGateway on shutdown.");
+                            Description.builder()
+                                    .text(
+                                            "Specifies whether to delete metrics from the PushGateway on shutdown."
+                                                    + " Flink will try its best to delete the metrics but this is not guaranteed. See %s for more details.",
+                                            LinkElement.link(
+                                                    "https://issues.apache.org/jira/browse/FLINK-13787",
+                                                    "here"))
+                                    .build());
 
     public static final ConfigOption<Boolean> FILTER_LABEL_VALUE_CHARACTER =
             ConfigOptions.key("filterLabelValueCharacters")