Field values are missing from widget of paragraph field

Problem/Motivation

When adding a social link field to a paragraph type, any saved field items aren't visible in the field widget

Steps to reproduce

1. Add some social links to a social link field on a paragraph type.
2. Save the paragraph.
3. Check the database, the field values are saved.
4. Reload the page. The saved field values aren't inserted in the widget.

Proposed resolution

Improve the $is_ajax_callback detection in SocialLinkWidget::getFormValues() to not give false positives when a paragraph form is opened in an AJAX callback.