Remove unused imports

**Cherry-pick to `5.4.x` & `5.3.x`**

Author: artembilan

spring-integration-core/src/main/java/org/springframework/integration/annotation/MessagingGateway.java

@@ -16,7 +16,6 @@
 
 package org.springframework.integration.annotation;
 
-import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;

spring-integration-http/src/main/java/org/springframework/integration/http/config/WebMvcIntegrationGraphCorsConfigurer.java

@@ -16,7 +16,6 @@
 
 package org.springframework.integration.http.config;
 
-import org.springframework.web.reactive.config.WebFluxConfigurer;
 import org.springframework.web.servlet.config.annotation.CorsRegistry;
 import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;