fix：【iot 物联网】增强 jdk8 的兼容性

yudao-framework/yudao-spring-boot-starter-web/src/main/java/cn/iocoder/yudao/framework/web/config/YudaoWebAutoConfiguration.java

@@ -50,7 +50,7 @@ public class YudaoWebAutoConfiguration {
 
             @Override
             public RequestMappingHandlerMapping getRequestMappingHandlerMapping() {
-                var mapping = new RequestMappingHandlerMapping();
+                RequestMappingHandlerMapping mapping = new RequestMappingHandlerMapping();
                 // 实例化时就带上前缀
                 mapping.setPathPrefixes(buildPathPrefixes(webProperties));
                 return mapping;