Remove mail links from references

[ceolinwill]

Describe the bug
When we add links to a post, they're added to the references at the bottom. However, email links shouldn't be added.

To Reproduce
Steps to reproduce the behavior:

1. Create a new post
2. Add a link to the content
3. Save your changes
4. Navigate to the recently created post
5. Scroll down to the references list
6. You'll see the email link there

Expected behavior
Email links shouldn't be included in the references.

Additional context

Remove existing email links from the database.