fix: Removed unnecessary JS & TS codes in linked_list.md (#852)

* fix: Removed unnecessary JS & TS codes in linked_list.md

* Update linked_list.md

---------

Co-authored-by: Yudong Jin <krahets@163.com>

docs/chapter_array_and_linkedlist/linked_list.md

@@ -96,8 +96,6 @@
     ```javascript title=""
     /* 链表节点类 */
     class ListNode {
-        val;
-        next;
         constructor(val, next) {
             this.val = (val === undefined ? 0 : val);       // 节点值
             this.next = (next === undefined ? null : next); // 指向下一节点的引用
@@ -546,9 +544,6 @@
     ```javascript title=""
     /* 双向链表节点类 */
     class ListNode {
-        val;
-        next;
-        prev;
         constructor(val, next, prev) {
             this.val = val  ===  undefined ? 0 : val;        // 节点值
             this.next = next  ===  undefined ? null : next;  // 指向后继节点的引用