Update README.md

Author: EndlessCheng

copypasta/template/interactive_problem/README.md

@@ -1,6 +1,6 @@
 # Interactive Problem Template
 
-You should implement this interface and use it both in `main.go` and `main_test.go`.
+To mock the IO part, implement this interface and use it both in `main.go` and `main_test.go`.
 
 ```go
 type interaction interface {
@@ -9,5 +9,3 @@ type interaction interface {
 	printAnswer(answer)
 }
 ``` 
-
-In this way we can mock the IO part.