Fix linter errors

app/helpers/issuables_helper.rb

 module IssuablesHelper
   def sidebar_gutter_toggle_icon
-    sidebar_gutter_collapsed? ? icon('angle-double-left', {'aria-hidden': 'true'}) : icon('angle-double-right', {'aria-hidden': 'true'})
+    sidebar_gutter_collapsed? ? icon('angle-double-left', { 'aria-hidden': 'true' }) : icon('angle-double-right', { 'aria-hidden': 'true' })
   end
 
   def sidebar_gutter_collapsed_class

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

@@ -9,7 +9,7 @@
       - if current_user
         %span.issuable-header-text.hide-collapsed.pull-left
           Todo
-      %a.gutter-toggle.pull-right.js-sidebar-toggle{ role: "button", href: "#", "aria-label" => "Toggle sidebar"  }
+      %a.gutter-toggle.pull-right.js-sidebar-toggle{ role: "button", href: "#", "aria-label" => "Toggle sidebar" }
         = sidebar_gutter_toggle_icon
       - if current_user
         %button.btn.btn-default.issuable-header-btn.pull-right.js-issuable-todo{ type: "button", "aria-label" => (todo.nil? ? "Add todo" : "Mark done"), data: { todo_text: "Add todo", mark_text: "Mark done", issuable_id: issuable.id, issuable_type: issuable.class.name.underscore, url: namespace_project_todos_path(@project.namespace, @project), delete_path: (dashboard_todo_path(todo) if todo) } }