Migrate invite_members_modal dropdown to listbox

What does this MR do and why?

It migrates the dropdown in invite_members_modal.vue from GlDropdown to GlCollapsibleListbox.

Screenshots or screen recordings

before	after

How to set up and validate locally

Steps to produce (or reach) the dropdown in the issue:

• Enable Feature.enable(:invite_members_for_task)

• Create a group

• Run the following

  group = Group.last
  user = group.owners.last
  Notify.in_product_marketing_email(user.id, group.id, :create, 0).deliver_now

• Open http://gdk.test:3000/rails/letter_opener/

• From the latest email, click "Invite them to help out." link below the main button.

• Select the role to be Developer+

• Tick "Create/import issues (tickets) to collaborate on ideas and plan work" checkbox

• The dropbox should appear 🎉

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.

Closes #384291 (closed)