fix for GRAILS-11481 "GrailsDispatcherServlet throws IllegalStateException when using forward() and render()"

 Change relates to removal of sitemesh filter in GRAILS-11357.

 The filter was removed but the ContentBufferingResponse was not being removed from the request. This causes GrailsOpenSessionInViewInterceptor to not close and unbind the session. This change ensures that the wrapped response is removed from the webRequest and thus the session unbound.