Update 06.4.md (#465)

修改名字错误

eBook/06.4.md

@@ -21,7 +21,7 @@ func function1() {
 }
 
 func function2() {
-	fmt.Printf("function2: Deferred until the end of the calling function!")
+	fmt.Printf("Function2: Deferred until the end of the calling function!")
 }
 ```
 
@@ -142,7 +142,7 @@ func trace(s string) { fmt.Println("entering:", s) }
 func untrace(s string) { fmt.Println("leaving:", s) }
 ```
 
-以下代码展示了何时调用两个函数：
+以下代码展示了何时调用这两个函数：
 
 示例 6.10 [defer_tracing.go](examples/chapter_6/defer_tracing.go):