Update the changelog for `get_approved_comments()` to reflect that the function was refactored to leverage `WP_Comment_Query` in [30098].

Also updates the `$args` parameter description with a reference to see `WP_Comment_Query` for argument information.

See #12668.


git-svn-id: https://develop.svn.wordpress.org/trunk@30109 602fd350-edb4-49c9-b593-d223f7449a82