更新 0203.移除链表元素.md python代码

使用更符合PEP8要求的代码规范来约束

problems/0203.移除链表元素.md

@@ -245,13 +245,15 @@ Python：
 #     def __init__(self, val=0, next=None):
 #         self.val = val
 #         self.next = next
+
 class Solution:
     def removeElements(self, head: ListNode, val: int) -> ListNode:
-        dummy_head = ListNode(next=head) #添加一个虚拟节点
+        dummy_head = ListNode(next=head)
         cur = dummy_head
-        while(cur.next!=None):
-            if(cur.next.val == val):
-                cur.next = cur.next.next #删除cur.next节点
+
+        while cur.next:
+            if cur.next.val == val:
+                cur.next = cur.next.next   # 删除下一个节点
             else:
                 cur = cur.next
         return dummy_head.next