Remove unnecessary import

tests/ui/mem_replace_macro.rs

@@ -4,8 +4,6 @@
 #[macro_use]
 extern crate macro_rules;
 
-use std::mem;
-
 macro_rules! take {
     ($s:expr) => {
         std::mem::replace($s, Default::default())

tests/ui/mem_replace_macro.stderr

@@ -1,5 +1,5 @@
 error: replacing a value of type `T` with `T::default()` is better expressed using `std::mem::take`
-  --> $DIR/mem_replace_macro.rs:11:9
+  --> $DIR/mem_replace_macro.rs:9:9
    |
 LL |         std::mem::replace($s, Default::default())
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^