Migrates legacy dropdown for groups_dropdown_filter

What does this MR do and why?

This MR migrates legacy GlDropdown to GlDisclosure according to OKR

Resolves #418083 (closed)

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After
before.mov	after.mov

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Go to a group
2. Select Analyze -> Productivity Analytics
3. Only way I was able to see the dropdown is by setting this line locally to v-if="hideGroupDropDown", because it seems that it is hardcoded to true on backend in ee/app/views/groups/analytics/productivity_analytics/show.html.haml

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 #418083 (closed)