Remove duplicated BS display properties from Wiki sidebar

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

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

 %aside.right-sidebar.right-sidebar-expanded.wiki-sidebar.js-wiki-sidebar.js-right-sidebar{ data: { "offset-top" => "50", "spy" => "affix" } }
   .sidebar-container
     .block.wiki-sidebar-header.gl-mb-3.w-100
-      %a.gutter-toggle.float-right.d-block.d-sm-block.d-md-none.js-sidebar-wiki-toggle{ href: "#" }
+      %a.gutter-toggle.float-right.d-block.d-md-none.js-sidebar-wiki-toggle{ href: "#" }
         = sprite_icon('chevron-double-lg-right', css_class: 'gl-icon')
 
       - if @wiki.container.is_a?(Project)