Update output of lint-type-overflow2.stderr to reflect its output from rustc -O.

(The fact that output differs under `opt-level=0` is an instance of rust-lang#55757.)

Author: pnkfelix

src/test/ui/lint/lint-type-overflow2.stderr

@@ -34,21 +34,15 @@ warning: literal out of range for f64
 LL |     let x =  1.7976931348623159e+308_f64; //~ warn: literal out of range for f64
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-warning: attempt to negate with overflow
+warning: this expression will panic at runtime
   --> $DIR/lint-type-overflow2.rs:19:18
    |
 LL |     let x2: i8 = --128; //~ warn: literal out of range for i8
-   |                  ^^^^^
+   |                  ^^^^^ attempt to negate with overflow
    |
 note: lint level defined here
   --> $DIR/lint-type-overflow2.rs:13:9
    |
 LL | #![warn(const_err)]
    |         ^^^^^^^^^
 
-warning: this expression will panic at runtime
-  --> $DIR/lint-type-overflow2.rs:19:18
-   |
-LL |     let x2: i8 = --128; //~ warn: literal out of range for i8
-   |                  ^^^^^ attempt to negate with overflow
-