Document default connection-pool-size for rest-client

Author: weltonrodrigo

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

@@ -150,6 +150,7 @@ public interface RestClientsConfig {
      * <p>
      * Can be overwritten by client-specific settings.
      */
+    @WithDefault("50")
     Optional<Integer> connectionPoolSize();
 
     /**