Remove outdated DNS caching docs from HTTP exporter (#39394)

These docs are out of date, now that we override the infinite DNS cache
within Elasticsearch. This commit completely removes this content, as
specific guidance is no longer needed here.

docs/reference/monitoring/http-export.asciidoc

@@ -91,27 +91,3 @@ monitoring clusters.
 
 For more information about the configuration options for the `http` exporter, 
 see <<http-exporter-settings>>.
-
-[float]
-[[http-exporter-dns]]
-==== Using DNS Hosts in HTTP Exporters
-
-{monitoring} runs inside of the JVM security manager. When the JVM has the
-security manager enabled, the JVM changes the duration so that it caches DNS
-lookups indefinitely (for example, the mapping of a DNS hostname to an IP 
-address). For this reason, if you are in an environment where the DNS response 
-might change from time-to-time (for example, talking to any load balanced cloud 
-provider), you are strongly discouraged from using DNS hostnames. 
-
-Alternatively, you can set the JVM security property `networkaddress.cache.ttl`, 
-which accepts values in seconds. This property must be set for the node's JVM that 
-uses {monitoring} for {es} when using DNS that can change IP addresses. If you 
-do not apply this setting, the connection consistently fails after the IP 
-address changes.
-
-IMPORTANT: JVM security properties are different than system properties. They
-cannot be set at startup via `-D` system property settings and instead they must 
-be set in code before the security manager has been setup _or_, more 
-appropriately, in the `$JAVA_HOME/lib/security/java.security` file.
-
-Restarting the node (and therefore the JVM) results in its cache being flushed.