hook_field_widget_multivalue_form_alter got deprecated in 9.2 and removed in Drupal 10. An implementation of this hook is found inside paragraphs_sets.module file. But the module is marked as D10 compatible. Need to check thoroughly whether this is affecting the functionality in D10 sites.
Removal details: https://www.drupal.org/node/3180429 →
Should implement alternative solution if functionality is getting affected.
Closed: works as designed
3.0
Code
Since the module is compatible to 9.3+ also and the hook is removed in Drupal 10 it should be left as is unless Paragraphs Sets is compatible to Drupal 10 only.