Fix unused_must_use warning for Box::from_raw

Author: noeddl

library/alloc/src/boxed.rs

@@ -952,7 +952,7 @@ impl<T: ?Sized> Box<T> {
     /// [`Layout`]: crate::Layout
     #[stable(feature = "box_raw", since = "1.4.0")]
     #[inline]
-    #[must_use = "call `drop(from_raw(ptr))` if you intend to drop the `Box`"]
+    #[must_use = "call `drop(Box::from_raw(ptr))` if you intend to drop the `Box`"]
     pub unsafe fn from_raw(raw: *mut T) -> Self {
         unsafe { Self::from_raw_in(raw, Global) }
     }

src/test/ui/lint/unused/must-use-box-from-raw.stderr

@@ -4,7 +4,7 @@ warning: unused return value of `Box::<T>::from_raw` that must be used
 LL |     Box::from_raw(ptr);
    |     ^^^^^^^^^^^^^^^^^^^
    |
-   = note: call `drop(from_raw(ptr))` if you intend to drop the `Box`
+   = note: call `drop(Box::from_raw(ptr))` if you intend to drop the `Box`
 note: the lint level is defined here
   --> $DIR/must-use-box-from-raw.rs:5:9
    |