docs: Fix expose path HTTP listener ports

The listener ports specified in the headings for the HTTP and HTTP2
examples do not match the ports in the corresponding service
registration configurations.

This commit changes the port specified in the heading for the HTTP
listener to match the port used in the service registration example.

In addition, the listener_port specified for the HTTP2 listener is
modified to match the port number specified in the heading.

website/source/docs/connect/registration/service-registration.html.md

@@ -267,7 +267,7 @@ registrations](/docs/agent/services.html#service-definition-parameter-case).
 }
 ```
 
-#### Expose an HTTP listener in Envoy at port 2150 that routes to an HTTP server listening at port 8080
+#### Expose an HTTP listener in Envoy at port 21500 that routes to an HTTP server listening at port 8080
 
 ```json
 {
@@ -293,7 +293,7 @@ registrations](/docs/agent/services.html#service-definition-parameter-case).
         "path": "/grpc.health.v1.Health/Check",
         "protocol": "http2",
         "local_path_port": 9090,
-        "listener_port": 21500
+        "listener_port": 21501
       }
     ]
   }