acquia_contenthub_unsubscribe module causes PHP warning for every form submission

Problem/Motivation

When the acquia_contenthub_unsubscribe module is installed, every time a form is submitted you receive the following warning during the redirection:

Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'acquia_contenthub_subscriber_sync_state_submit' not found or invalid function name in Drupal\Core\Form\FormSubmitter->executeSubmitHandlers() (line 114 of /var/www/docroot/core/lib/Drupal/Core/Form/FormSubmitter.php).

This is because the function acquia_contenthub_subscriber_sync_state_submit is not declared anywhere.

Steps to reproduce

1. Enable the acquia_contenthub_unsubscribe module.
2. Submit any form.
3. Witness the warning.

Proposed resolution

I believe the intent was to include the acquia_contenthub_unsubscribe_sync_state_submit submit handler located beneath the form alter, rather than the above mentioned submit handler in the acquia_contenthub_subscriber namespace. Seems like a copy/paste error?

Remaining tasks

User interface changes

API changes

Data model changes