Document default per-client connection-pool-size for rest-cliet.

Author: weltonrodrigo

extensions/resteasy-classic/rest-client-config/runtime/src/main/java/io/quarkus/restclient/config/RestClientsConfig.java

@@ -543,6 +543,7 @@ default Optional<String> uriReload() {
         /**
          * The size of the connection pool for this client.
          */
+        @WithDefault("50")
         Optional<Integer> connectionPoolSize();
 
         /**