lib: changed var to const in linkedlist

PR-URL: #8609
Reviewed-By: Brian White <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Michaël Zasso <[email protected]>

Author: AdriVanHoudt

lib/_linklist.js

@@ -17,7 +17,7 @@ exports.peek = peek;
 
 // remove the most idle item from the list
 function shift(list) {
-  var first = list._idlePrev;
+  const first = list._idlePrev;
   remove(first);
   return first;
 }