Fix a warning on no_std and the expected output for Result

Since invalid `Result<T>` output changed, the expected file had to be
updated.

The output actually got better, since now the location of the actual
declaration of the offending struct is also shown, not only the usage.

src/result.rs

@@ -4,6 +4,7 @@
 use alloc::boxed::Box;
 use alloc::string::ToString;
 use core::fmt::Display;
+#[cfg(feature = "std")]
 use core::mem::MaybeUninit;
 use core::ptr::NonNull;
 use core::slice;

tests/ui/result_no_display.stderr

@@ -1,8 +1,18 @@
-error[E0277]: `NonError` doesn't implement `std::fmt::Display`
+error[E0599]: the method `to_cxx_exception` exists for reference `&NonError`, but its trait bounds were not satisfied
  --> tests/ui/result_no_display.rs:4:19
   |
 4 |         fn f() -> Result<()>;
-  |                   ^^^^^^^^^^ `NonError` cannot be formatted with the default formatter
+  |                   ^^^^^^^^^^ method cannot be called on `&NonError` due to unsatisfied trait bounds
+...
+8 | pub struct NonError;
+  | ------------------- doesn't satisfy `NonError: std::fmt::Display`
   |
-  = help: the trait `std::fmt::Display` is not implemented for `NonError`
-  = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
+  = note: the following trait bounds were not satisfied:
+          `NonError: std::fmt::Display`
+          which is required by `&NonError: ToCxxExceptionDefault`
+note: the trait `std::fmt::Display` must be implemented
+ --> $RUST/core/src/fmt/mod.rs
+  |
+  | pub trait Display {
+  | ^^^^^^^^^^^^^^^^^
+  = note: this error originates in the macro `::cxx::map_rust_error_to_cxx_exception` (in Nightly builds, run with -Z macro-backtrace for more info)