Make it clear which value is discarded

Author: nagisa

src/libcore/result.rs

@@ -330,7 +330,7 @@ impl<T, E> Result<T, E> {
     /// Convert from `Result<T, E>` to `Option<E>`
     ///
     /// Converts `self` into an `Option<E>`, consuming `self`,
-    /// and discarding the value, if any.
+    /// and discarding the success value, if any.
     ///
     /// # Examples
     ///