Correction of problem 1 in vector.md

```v1``` cannot be referred if the ownership of ```v``` is moved to ```fn is_vec(v: &Vec<u8>)```

en/src/collections/vector.md

@@ -9,26 +9,26 @@ fn main() {
     let arr: [u8; 3] = [1, 2, 3];
     
     let v = Vec::from(arr);
-    is_vec(v);
+    is_vec(&v);
 
     let v = vec![1, 2, 3];
-    is_vec(v);
+    is_vec(&v);
 
     // vec!(..) and vec![..] are same macros, so
     let v = vec!(1, 2, 3);
-    is_vec(v);
+    is_vec(&v);
     
     // In code below, v is Vec<[u8; 3]> , not Vec<u8>
     // USE Vec::new and `for` to rewrite the below code 
     let v1 = vec!(arr);
-    is_vec(v1);
+    is_vec(&v1);
  
     assert_eq!(v, v1);
 
     println!("Success!");
 }
 
-fn is_vec(v: Vec<u8>) {}
+fn is_vec(v: &Vec<u8>) {}
 ```
 
 
@@ -241,4 +241,4 @@ fn main() {
         ip.display();
     }
 }
-```
+```