GH-3004: Revert scope of handler factories

See #3004

spring-projects/spring-framework#23352
is now resolved so the `DefaultMessageHandlerMethodFactory` can be
singletons.

Author: garyrussell

spring-integration-core/src/main/java/org/springframework/integration/config/DefaultConfiguringBeanFactoryPostProcessor.java

@@ -38,7 +38,6 @@
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.BeanDefinitionHolder;
 import org.springframework.beans.factory.config.BeanFactoryPostProcessor;
-import org.springframework.beans.factory.config.ConfigurableBeanFactory;
 import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
 import org.springframework.beans.factory.config.PropertiesFactoryBean;
 import org.springframework.beans.factory.config.RuntimeBeanReference;
@@ -518,8 +517,6 @@ private void registerMessageHandlerMethodFactory() {
 		if (!this.beanFactory.containsBean(IntegrationContextUtils.MESSAGE_HANDLER_FACTORY_BEAN_NAME)) {
 			BeanDefinitionBuilder messageHandlerMethodFactoryBuilder =
 					createMessageHandlerMethodFactoryBeanDefinition(false);
-			// TODO: https://github.com/spring-projects/spring-framework/issues/23352
-			messageHandlerMethodFactoryBuilder.setScope(ConfigurableBeanFactory.SCOPE_PROTOTYPE);
 			this.registry.registerBeanDefinition(IntegrationContextUtils.MESSAGE_HANDLER_FACTORY_BEAN_NAME,
 					messageHandlerMethodFactoryBuilder.getBeanDefinition());
 		}
@@ -529,8 +526,6 @@ private void registerListMessageHandlerMethodFactory() {
 		if (!this.beanFactory.containsBean(IntegrationContextUtils.LIST_MESSAGE_HANDLER_FACTORY_BEAN_NAME)) {
 			BeanDefinitionBuilder messageHandlerMethodFactoryBuilder =
 					createMessageHandlerMethodFactoryBeanDefinition(true);
-			// TODO: https://github.com/spring-projects/spring-framework/issues/23352
-			messageHandlerMethodFactoryBuilder.setScope(ConfigurableBeanFactory.SCOPE_PROTOTYPE);
 			this.registry.registerBeanDefinition(IntegrationContextUtils.LIST_MESSAGE_HANDLER_FACTORY_BEAN_NAME,
 					messageHandlerMethodFactoryBuilder.getBeanDefinition());
 		}