Fix backend filtering in RTE autocomplete

What does this MR do and why?

This fixes a regression where backend filtering wasn't working properly in the rich-text editor because the options weren't passed in correctly.

This is a regression from !172104 (merged)

References

Please include cross links to any resources that are relevant to this MR. This will give reviewers and future readers helpful context to give an efficient review of the changes introduced.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

1. Type @ in the rich-text editor
2. You should see the search=xxx param in the network request being made and it should make a new request as you type