rustdoc-search: add unbox flag to Result aliases

Fixes rust-lang#139665

Author: notriddle

std/src/io/error.rs

@@ -48,6 +48,7 @@ use crate::{error, fmt, result, sys};
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(search_unbox))]
 pub type Result<T> = result::Result<T, Error>;
 
 /// The error type for I/O operations of the [`Read`], [`Write`], [`Seek`], and

std/src/thread/mod.rs

@@ -1676,6 +1676,7 @@ impl fmt::Debug for Thread {
 /// [`Result`]: crate::result::Result
 /// [`std::panic::resume_unwind`]: crate::panic::resume_unwind
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(bootstrap), doc(search_unbox))]
 pub type Result<T> = crate::result::Result<T, Box<dyn Any + Send + 'static>>;
 
 // This packet is used to communicate the return value between the spawned