Start using #[diagnostic::do_not_recommend] in the standard library

This commit starts using `#[diagnostic::do_not_recommend]` in the
standard library to improve some error messages. In this case we just
hide a certain nightly only impl as suggested in #121521

library/core/src/lib.rs

@@ -165,6 +165,7 @@
 #![feature(const_unsafecell_get_mut)]
 #![feature(const_waker)]
 #![feature(coverage_attribute)]
+#![feature(do_not_recommend)]
 #![feature(duration_consts_float)]
 #![feature(internal_impls_macro)]
 #![feature(ip)]

library/core/src/option.rs

@@ -2507,6 +2507,7 @@ impl<T> ops::FromResidual for Option<T> {
     }
 }
 
+#[diagnostic::do_not_recommend]
 #[unstable(feature = "try_trait_v2_yeet", issue = "96374")]
 impl<T> ops::FromResidual<ops::Yeet<()>> for Option<T> {
     #[inline]

library/core/src/result.rs

@@ -1990,7 +1990,7 @@ impl<T, E, F: From<E>> ops::FromResidual<Result<convert::Infallible, E>> for Res
         }
     }
 }
-
+#[diagnostic::do_not_recommend]
 #[unstable(feature = "try_trait_v2_yeet", issue = "96374")]
 impl<T, E, F: From<E>> ops::FromResidual<ops::Yeet<E>> for Result<T, F> {
     #[inline]