Remove FF `gl_listbox_for_sort_dropdowns`

What does this MR do and why?

Removed the gl_listbox_for_sort_dropdowns FF and cleaned up unnecessary code. In the scope of this epic &8826 (closed) all instances of gl_redirect_listbox_tag proved to work fine with GlListbox under the hood instead of the GlDropdown. So now we can confidently switch to the GlListbox unconditionally.

How to set up and validate locally

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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.

Related to #364715 (closed)