Remove unused sections

app/assets/stylesheets/pages/boards.scss

@@ -747,12 +747,6 @@
   }
 }
 
-.board-milestone-footer-content {
-  padding-left: 12px;
-  padding-right: 12px;
-  color: $gl-gray-dark;
-}
-
 .board-config-modal {
   width: 440px;
 

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

 - boards_page = controller.controller_name == 'boards'
-- board = local_assigns[:board]
 
 .issues-filters
   .issues-details-filters.row-content-block.second-block
@@ -20,7 +19,7 @@
             placeholder: "Search assignee", data: { any_user: "Any Assignee", first_user: current_user&.username, null_user: true, current_user: true, project_id: @project&.id, group_id: @group&.id, selected: params[:assignee_id], field_name: "assignee_id", default_label: "Assignee" } })
 
         .filter-item.inline.milestone-filter
-          = render "shared/issuable/milestone_dropdown", selected: finder.milestones.try(:first), name: :milestone_title, show_any: true, show_upcoming: true, board: board, show_started: true
+          = render "shared/issuable/milestone_dropdown", selected: finder.milestones.try(:first), name: :milestone_title, show_any: true, show_upcoming: true, show_started: true
 
         .filter-item.inline.labels-filter
           = render "shared/issuable/label_dropdown", selected: selected_labels, use_id: false, selected_toggle: params[:label_name], data_options: { field_name: "label_name[]" }

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

 - project = @target_project || @project
 - extra_class = extra_class || ''
 - show_menu_above = show_menu_above || false
-- board = local_assigns[:board]
-- selected = board.try(:milestone) || local_assigns[:selected]
+- selected = local_assigns.fetch(:selected, nil)
 
 - selected_text = selected.try(:title) || params[:milestone_title]
 - dropdown_title = local_assigns.fetch(:dropdown_title, "Filter by milestone")
@@ -22,7 +21,3 @@
             Manage milestones
           - else
             View milestones
-    - if board
-      %p.board-milestone-footer-content.js-milestone-footer-content{ style: "display: none;" }
-        This board's milestone has been set in its configuration.
-        Edit this value under the board menu.