Improve the inline documentation for `image_edit_apply_changes()`.

Including:
* Add a correct type (array) for the `$changes` parameter
* Add the `@since` version
* Add proper descriptions for both parameters and the return value.

Props tillkruess for the initial patch.
See #30508.


git-svn-id: https://develop.svn.wordpress.org/trunk@30644 602fd350-edb4-49c9-b593-d223f7449a82