fix post excerpt typo - Githubissues

Context

fix a typo for child pages post excerpt. See Reports https://wordpress.org/support/topic/excerpt-problem-9/ and #369

Fixes #369

This PR can be summarized in the following changelog entry:

Fixes a bug where cloning an attachment did not copy its description as expected.
Fixes a bug where cloning an attachment did not copy its caption as expected. Props to @masteradhoc.

This PR can be acceptance tested by following these steps:

in the Duplicate Post settings, under "Post/page elements to copy", select "Attachments" and save
Create/edit a post
add an image to it by uploading a new one
make sure to edit the image in the media library modal and add alt. text, caption and decription.
save the post
clone the post
check the media library page: you should get 2 copies of the image you uploaded
edit both of them and check that both have the same values for alt. text, caption and description.
- without this PR, caption and description were not copied at all.

[ ] Changes should be tested with the browser console open
[ ] Changes should be tested on different posts/pages/taxonomies/custom post types/custom taxonomies
[ ] Changes should be tested on different editors (Default Block/Gutenberg/Classic/Elementor/other)
[ ] Changes should be tested on different browsers
[ ] Changes should be tested on multisite

QA can test this PR by following these steps:

This PR affects the following parts of the plugin, which may require extra testing:

[ ] This PR changes the UI in the plugin. I have added the 'UI change' label to this PR.

[ ] I have written documentation for this change. For example, comments in the Relevant technical choices, comments in the code, documentation on Confluence / shared Google Drive / Yoast developer portal, or other.

[ ] No innovation project is applicable for this PR.
[ ] This PR falls under an innovation project. I have attached the innovation label and noted the work hours.

Fixes #