Update ui tests to 2018 edition

test_suite/tests/ui/malformed/bound.rs

@@ -1,5 +1,4 @@
-#[macro_use]
-extern crate serde_derive;
+use serde_derive::Serialize;
 
 #[derive(Serialize)]
 struct S {

test_suite/tests/ui/malformed/bound.stderr

@@ -1,7 +1,7 @@
 error: malformed bound attribute, expected `bound(serialize = ..., deserialize = ...)`
- --> $DIR/bound.rs:6:19
+ --> $DIR/bound.rs:5:19
   |
-6 |     #[serde(bound(unknown))]
+5 |     #[serde(bound(unknown))]
   |                   ^^^^^^^
 
 error: aborting due to previous error

test_suite/tests/ui/malformed/rename.rs

@@ -1,5 +1,4 @@
-#[macro_use]
-extern crate serde_derive;
+use serde_derive::Serialize;
 
 #[derive(Serialize)]
 struct S {

test_suite/tests/ui/malformed/rename.stderr

@@ -1,7 +1,7 @@
 error: malformed rename attribute, expected `rename(serialize = ..., deserialize = ...)`
- --> $DIR/rename.rs:6:20
+ --> $DIR/rename.rs:5:20
   |
-6 |     #[serde(rename(unknown))]
+5 |     #[serde(rename(unknown))]
   |                    ^^^^^^^
 
 error: aborting due to previous error