refactor: Replace 结点 with 节点 (#452)

* Replace 结点 with 节点
Update the footnotes in the figures

* Update mindmap

* Reduce the size of the mindmap.png

codes/go/chapter_tree/binary_tree_bfs_test.go

@@ -20,5 +20,5 @@ func TestLevelOrder(t *testing.T) {
 
 	// 层序遍历
 	nums := levelOrder(root)
-	fmt.Println("\n层序遍历的结点打印序列 =", nums)
+	fmt.Println("\n层序遍历的节点打印序列 =", nums)
 }