Replace deprecated/removed form alter hook with D10 version

[jastraat]

hook_field_widget_multivalue_form_alter was deprecated in Drupal 9.2 and removed in Drupal 10.

https://api.drupal.org/api/drupal/core%21modules%21field%21field.api.php/function/hook_field_widget_multivalue_form_alter/9

This hook was used to identify json form widget forms and in its absence, json_form_widget_file_submit() is not run on node form submission. The result is that the files uploaded through the node form are left in temporary status and the file usage table also not updated. This can result in data loss when temporary files are cleaned up.

• Test coverage exists
• Documentation exists

QA Steps

• Create a dataset through the node form UI and make sure to upload a distribution file.
• After submitting the form, visit admin/content/files and confirm that the file has a status of "Permanent"