Adjust clippy tests to account for unreachable! changes

Author: Mark-Simulacrum

src/tools/clippy/tests/ui/panic_in_result_fn.stderr

@@ -48,7 +48,7 @@ note: return Err() instead of panicking
    |
 LL |         unreachable!();
    |         ^^^^^^^^^^^^^^
-   = note: this error originates in the macro `unreachable` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `$crate::panic::unreachable_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: used `unimplemented!()`, `unreachable!()`, `todo!()`, `panic!()` or assertion in a function that returns `Result`
   --> $DIR/panic_in_result_fn.rs:21:5

src/tools/clippy/tests/ui/panicking_macros.stderr

@@ -75,23 +75,22 @@ LL |     unreachable!();
    |     ^^^^^^^^^^^^^^
    |
    = note: `-D clippy::unreachable` implied by `-D warnings`
-   = note: this error originates in the macro `unreachable` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: usage of the `unreachable!` macro
   --> $DIR/panicking_macros.rs:33:5
    |
 LL |     unreachable!("message");
    |     ^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: this error originates in the macro `$crate::unreachable` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `$crate::panic::unreachable_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: usage of the `unreachable!` macro
   --> $DIR/panicking_macros.rs:34:5
    |
 LL |     unreachable!("{} {}", "panic with", "multiple arguments");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: this error originates in the macro `unreachable` (in Nightly builds, run with -Z macro-backtrace for more info)
+   = note: this error originates in the macro `$crate::panic::unreachable_2021` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: `panic` should not be present in production code
   --> $DIR/panicking_macros.rs:40:5
@@ -120,8 +119,6 @@ error: usage of the `unreachable!` macro
    |
 LL |     unreachable!();
    |     ^^^^^^^^^^^^^^
-   |
-   = note: this error originates in the macro `unreachable` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: aborting due to 16 previous errors