Add reason why port 53 is not used by default (#19222)

* Update dns-configuration.mdx

* Update website/content/docs/services/discovery/dns-configuration.mdx

Co-authored-by: Tu Nguyen <im2nguyen@users.noreply.github.com>

website/content/docs/services/discovery/dns-configuration.mdx

@@ -16,7 +16,7 @@ The Consul DNS is the primary interface for querying records when Consul service
 By default, the Consul DNS listens for queries at `127.0.0.1:8600` and uses the `consul` domain. Specify the following parameters in the agent configuration to determine DNS behavior when querying services:
 
 - [`client_addr`](/consul/docs/agent/config/config-files#client_addr)
-- [`ports.dns`](/consul/docs/agent/config/config-files#dns_port)
+- [`ports.dns`](/consul/docs/agent/config/config-files#dns_port) : Consul does not use port `53`, which is typically reserved for the default port for DNS resolvers, by default because it requires an escalated privilege to bind to. 
 - [`recursors`](/consul/docs/agent/config/config-files#recursors)
 - [`domain`](/consul/docs/agent/config/config-files#domain)
 - [`alt_domain`](/consul/docs/agent/config/config-files#alt_domain)