refactor: 右上角的帮助文档，修改为新页面打开

--bug=1004972 --user=王振 【github#4495】右上角的帮助文档，修改为新开页面，不要当前页面跳转。 https://www.tapd.cn/55049933/s/1024900

frontend/src/business/components/common/head/HeaderUser.vue

@@ -84,7 +84,7 @@ export default {
           this.$refs.aboutUs.open();
           break;
         case "help":
-          window.location.href = "https://metersphere.io/docs/index.html";
+          window.open('https://metersphere.io/docs/index.html', "_blank");
           break;
         case "ApiHelp":
           window.open('/swagger-ui/index.html?configUrl=/v3/api-docs/swagger-config', "_blank");