Fixed duplicate new milestone buttons in new navigation

Closes #35454

app/assets/stylesheets/framework/nav.scss

@@ -182,6 +182,12 @@
       }
     }
 
+    &.nav-controls-new-nav {
+      > .dropdown {
+        margin-right: 0;
+      }
+    }
+
     > .btn-grouped {
       float: none;
     }

app/views/projects/milestones/index.html.haml

 - @no_container = true
 - page_title 'Milestones'
 
-- if show_new_nav?
+- if show_new_nav? && can?(current_user, :admin_milestone, @project)
   - content_for :breadcrumbs_extra do
     = link_to "New milestone", new_namespace_project_milestone_path(@project.namespace, @project), class: 'btn btn-new', title: 'New milestone'
 
@@ -11,10 +11,10 @@
   .top-area
     = render 'shared/milestones_filter', counts: milestone_counts(@project.milestones)
 
-    .nav-controls
+    .nav-controls{ class: ("nav-controls-new-nav" if show_new_nav?) }
       = render 'shared/milestones_sort_dropdown'
       - if can?(current_user, :admin_milestone, @project)
-        = link_to new_project_milestone_path(@project), class: 'btn btn-new', title: 'New milestone' do
+        = link_to new_project_milestone_path(@project), class: "btn btn-new #{("visible-xs" if show_new_nav?)}", title: 'New milestone' do
           New milestone
 
   .milestones

changelogs/unreleased/new-nav-duplicated-new-milestone-buttons.yml

+---
+title: Fixed duplicate new milestone buttons when new navigation is turned on
+merge_request:
+author: