Used const instead of let

Author: dzz007

lib/plugins/leetcode.js

@@ -535,8 +535,7 @@ plugin.login = function(user, cb) {
 
 function parseCookie(cookie, body, cb) {
   const SessionPattern = /LEETCODE_SESSION=(.+?)(;|$)/;
-  let csrfPattern;
-  csrfPattern = /csrftoken=(.+?)(;|$)/;
+  const csrfPattern = /csrftoken=(.+?)(;|$)/;
   const reCsrfResult = csrfPattern.exec(cookie);
   const reSessionResult = SessionPattern.exec(cookie);
   if (reSessionResult === null || reCsrfResult === null) {