Fix doctests.

Author: zachs18

library/alloc/src/rc.rs

@@ -1320,7 +1320,7 @@ impl<T: ?Sized, A: Allocator> Rc<T, A> {
     ///
     /// let x = Rc::new_in("hello".to_owned(), System);
     /// let (ptr, alloc) = Rc::into_raw_with_allocator(x);
-    /// assert_eq!(unsafe { &*x }, "hello");
+    /// assert_eq!(unsafe { &*ptr }, "hello");
     /// let x = unsafe { Rc::from_raw_in(ptr, alloc) };
     /// assert_eq!(&*x, "hello");
     /// ```

library/alloc/src/sync.rs

@@ -1471,6 +1471,7 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
     ///
     /// let x = Arc::new_in("hello".to_owned(), System);
     /// let (ptr, alloc) = Arc::into_raw_with_allocator(x);
+    /// assert_eq!(unsafe { &*ptr }, "hello");
     /// let x = unsafe { Arc::from_raw_in(ptr, alloc) };
     /// assert_eq!(&*x, "hello");
     /// ```