Remove project_list_filter_bar unused feature

What does this MR do and why?

Related to #321404 (closed)

This feature was introduced behind a feature flag in %11.11 but has never been rolled out.

The next logical step for the project list will be a migration to Vue and likely introduction of the GlFilteredSearch.

This MR removes the unused feature.

How to set up and validate locally

Visit http://gdk.test:3000/dashboard/projects and ensure things look and are behaving AOK

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.