Clarify that `Cow::into_owned` returns owned data
Two sections of the `Cow::into_owned` docs imply that `into_owned` returns a `Cow`. Clarify that it returns the underlying owned object, either cloned or extracted from the `Cow`.
///
/// # Examples
///
- /// Calling `into_owned` on a `Cow::Borrowed` clones the underlying data
- /// and becomes a `Cow::Owned`:
+ /// Calling `into_owned` on a `Cow::Borrowed` returns a clone of the borrowed data:
///
/// ```
/// use std::borrow::Cow;
/// );
/// ```
///
- /// Calling `into_owned` on a `Cow::Owned` is a no-op:
+ /// Calling `into_owned` on a `Cow::Owned` returns the owned data. The data is moved out of the
+ /// `Cow` without being cloned.
///
/// ```
/// use std::borrow::Cow;