Add @ConditionalOnMissing bean to FilteringWebHandler (#2308)

Co-authored-by: Tomasz Rup <tomasz.rup@comarch.com>

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

@@ -258,6 +258,7 @@ public class GatewayAutoConfiguration {
 	}
 
 	@Bean
+	@ConditionalOnMissingBean
 	public FilteringWebHandler filteringWebHandler(List<GlobalFilter> globalFilters) {
 		return new FilteringWebHandler(globalFilters);
 	}