Description of the Change

When a post is deleted in ElasticPress, we see that two queries are sent to Elasticsearch to delete that post. Since they are duplicated, at least one of those queries always fails. This happens because we are sending the ep_delete_post signal twice.

This PR gets rid of that duplication.

Verification Process

We have this change deployed and running in production at VIP and it has drastically reduced the errors derived from calling the deletion of a post twice.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Changelog Entry

• [Fixed] Prevents a post from being attempted to delete twice.