Fix test file

Author: geoffreycopin

tests/ui/unnecessary_cast_fixable.fixed

@@ -30,6 +30,6 @@ fn main() {
 
     1.0 as u16;
 
-    -1_i32;
-    -1.0_f32;
+    let _ = -1_i32;
+    let _ = -1.0_f32;
 }

tests/ui/unnecessary_cast_fixable.rs

@@ -30,6 +30,6 @@ fn main() {
 
     1.0 as u16;
 
-    -1 as i32;
-    -1.0 as f32;
+    let _ = -1 as i32;
+    let _ = -1.0 as f32;
 }

tests/ui/unnecessary_cast_fixable.stderr

@@ -61,16 +61,16 @@ LL |     0.5 as f32;
    |     ^^^^^^^^^^ help: try: `0.5_f32`
 
 error: casting integer literal to `i32` is unnecessary
-  --> $DIR/unnecessary_cast_fixable.rs:33:5
+  --> $DIR/unnecessary_cast_fixable.rs:33:13
    |
-LL |     -1 as i32;
-   |     ^^^^^^^^^ help: try: `-1_i32`
+LL |     let _ = -1 as i32;
+   |             ^^^^^^^^^ help: try: `-1_i32`
 
 error: casting float literal to `f32` is unnecessary
-  --> $DIR/unnecessary_cast_fixable.rs:34:5
+  --> $DIR/unnecessary_cast_fixable.rs:34:13
    |
-LL |     -1.0 as f32;
-   |     ^^^^^^^^^^^ help: try: `-1.0_f32`
+LL |     let _ = -1.0 as f32;
+   |             ^^^^^^^^^^^ help: try: `-1.0_f32`
 
 error: aborting due to 12 previous errors