045c5cd populate dropdown-menu when button is clicked, not upon page load

Authored and Committed by karsten 2 months ago
    populate dropdown-menu when button is clicked, not upon page load
    
    fixes #3599
    every page related to a git repository has a pull-request button that
    opens a dropdown-menu. This menu is populated when the page loads, even
    when creating a PR might not be the intention of visiting that page.
    
    Signed-off-by: Karsten Hopp <karsten@redhat.com>