modify the answer of 3.4

Author: felix0913

README.md

@@ -353,8 +353,8 @@
     def str2dict(str1):
         dict1 = {}
         for iterms in str1.split('|'):
-            key,value = iterms.split(':'):
-                dict1[key] = value
+            key,value = iterms.split(':')
+            dict1[key] = value
         return dict1
 ```
 ## 3.5 请按alist中元素的age由小到大排序