fixed 406f1036 from https://gitee.com/zengyawen/docs/pulls/14619

update zh-cn/application-dev/security/cert-guidelines.md.
Signed-off-by: Nzengyawen <zengyawen1@huawei.com>

zh-cn/application-dev/security/cert-guidelines.md

@@ -441,7 +441,7 @@ function crlEntrySample() {
     }
 
     // 获取被吊销证书的序列号
-    let serialNumber = crlEntry.getSerialNumber();
+    serialNumber = crlEntry.getSerialNumber();
     
     // 获取被吊销证书的吊销日期
     try {