Use local assigns to get the dropdown title

app/views/shared/issuable/_milestone_dropdown.html.haml

@@ -2,7 +2,7 @@
 - extra_class = extra_class || ''
 - show_menu_above = show_menu_above || false
 - selected_text = selected.try(:title)
-- dropdown_title = dropdown_title || "Filter by milestone"
+- dropdown_title = local_assigns.fetch(:dropdown_title, "Filter by milestone")
 - if selected.present?
   = hidden_field_tag(name, name == :milestone_title ? selected.title : selected.id)
 = dropdown_tag(milestone_dropdown_label(selected_text), options: { title: dropdown_title, toggle_class: "js-milestone-select js-filter-submit #{extra_class}", filter: true, dropdown_class: "dropdown-menu-selectable dropdown-menu-milestone",