doc: Reword deprecation message of MetadataExt::as_raw_stat

Author: tesuji

src/libstd/os/linux/fs.rs

@@ -34,9 +34,10 @@ pub trait MetadataExt {
     /// }
     /// ```
     #[stable(feature = "metadata_ext", since = "1.1.0")]
-    #[rustc_deprecated(since = "1.8.0",
-                       reason = "deprecated in favor of the accessor \
-                                 methods of this trait")]
+    #[rustc_deprecated(
+        since = "1.8.0",
+        reason = "other methods of this trait are now prefered"
+    )]
     #[allow(deprecated)]
     fn as_raw_stat(&self) -> &raw::stat;