Remove "intermittent" wording from ReadDir

Author: ChrisDenton

library/std/src/fs.rs

@@ -153,9 +153,8 @@ pub struct Metadata(fs_imp::FileAttr);
 /// dependent.
 ///
 /// # Errors
-///
-/// This [`io::Result`] will be an [`Err`] if there's some sort of intermittent
-/// IO error during iteration.
+/// This [`io::Result`] will be an [`Err`] if an error occurred while fetching
+/// the next entry from the OS.
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Debug)]
 pub struct ReadDir(fs_imp::ReadDir);