Describe the bug
When BoldGrid Easy SEO is active, each post and page has two canonical links. This is considered detrimental for SEO.

To Reproduce
Steps to reproduce the behavior:

1. Launch WordPress with BoldGrid Easy SEO
   https://www.boldgrid.com/central/cloud-wordpress/try?theme=twentynineteen&plugins=boldgrid-easy-seo
2. View the source of any page or post
3. Ctrl-F for "canonical"

Expected behavior
If the user inputs a Canonical link into BoldGrid Easy SEO, it should replace the existing Canonical link, rather than adding a second one.
If the user leaves the Canonical link blank, the Core Canonical URL should be left as-is.

Screenshots

Additional context
This issue came up during a routine SEO Audit of the BoldGrid.com Support Center website.