Remove target ref switcher.

app/views/projects/tree/_tree_header.html.haml

 .tree-ref-container
   .tree-ref-holder
     = render 'shared/ref_switcher', destination: 'tree', path: @path
-    - if show_new_repo?
-      .tree-ref-target-holder.js-tree-ref-target-holder
-        = icon('long-arrow-right', title: 'to target branch')
-        = render 'shared/target_switcher', destination: 'tree', path: @path
   - unless show_new_repo?
     = render 'projects/tree/old_tree_header'

app/views/shared/_target_switcher.html.haml

-- dropdown_toggle_text = @ref || @project.default_branch
-= form_tag nil, method: :get, class: "project-refs-form project-refs-target-form" do
-  = hidden_field_tag :destination, destination
-  - if defined?(path)
-    = hidden_field_tag :path, path
-  - @options && @options.each do |key, value|
-    = hidden_field_tag key, value, id: nil
-  .dropdown
-    = dropdown_toggle dropdown_toggle_text, { toggle: "dropdown", selected: dropdown_toggle_text, ref: @ref, refs_url: refs_project_path(@project, find: ['branches']), field_name: 'ref', input_field_name: 'new-branch', submit_form_on_click: true, visit: false }, { toggle_class: "js-project-refs-dropdown" }
-    .dropdown-menu.dropdown-menu-selectable.git-revision-dropdown{ class: ("dropdown-menu-align-right" if local_assigns[:align_right]) }
-      = dropdown_title _("Create a new branch")
-      = dropdown_input _("Create a new branch")
-      = dropdown_title _("Select existing branch"), options: {close: false}
-      = dropdown_filter _("Search branches and tags")
-      = dropdown_content
-      = dropdown_loading