fix(graph): enhance the judgment of corner case for removeEdge functions

[ztkuaikuai]

9.2.2 基于邻接表的实现中 JS 和 TS 代码片段 removeEdge 函数如果传入的两个顶点不为邻接点，那么在对应邻接表 adjList 中查找不到对应的顶点，返回 -1，继续执行则会删除顶点的邻接顶点表最后一项，即 splice(-1, 1)。

通过添加边界条件判断两顶点是否为邻接点修复此问题。

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相关代码控制台输出：

初始化后，图为
邻接表 =
1: 3,5
3: 1,2
2: 3,5,4
5: 2,1,4
4: 2,5

添加边 1-2 后，图为
邻接表 =
1: 3,5,2
3: 1,2
2: 3,5,4,1
5: 2,1,4
4: 2,5

删除边 1-3 后，图为
邻接表 =
1: 5,2
3: 2
2: 3,5,4,1
5: 2,1,4
4: 2,5

添加顶点 6 后，图为
邻接表 =
1: 5,2
3: 2
2: 3,5,4,1
5: 2,1,4
4: 2,5
6:

删除顶点 3 后，图为
邻接表 =
1: 5,2
2: 5,4,1
5: 2,1,4
4: 2,5
6: