Merge pull request #70 from hetykai/patch-1

Update 07.4.md

eBook/07.4.md

@@ -58,7 +58,7 @@ slice 可以反复扩展直到占据整个相关数组。
 
 另一个例子：
 
-	var ar = [10]int{0,1,2,3,4,5,6,,7,8,9}
+	var ar = [10]int{0,1,2,3,4,5,6,7,8,9}
 	var a = ar[5:7] // reference to subarray {5,6} - len(a) is 2 and cap(a) is 5
 
 将a重新分片