Fix WebClientAdapter.createHttpServiceProxyFactory() example in ref docs
Fix WebClientAdapter.createHttpServiceProxyFactory() example in ref docs

* Remove build() call
* Add call to afterPropertiesSet()

Closes gh-28753
spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework,spring-projects/spring-framework