Replace .group-buttons with display properties

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

app/assets/stylesheets/framework/mobile.scss

@@ -37,10 +37,6 @@
     }
   }
 
-  .group-buttons {
-    display: none;
-  }
-
   .container .title {
     padding-left: 15px !important;
   }

app/views/groups/_home_panel.html.haml

@@ -12,6 +12,6 @@
         = markdown_field(@group, :description)
 
     - if current_user
-      .group-buttons
+      .group-buttons.d-none.d-sm-block
         = render 'shared/members/access_request_buttons', source: @group
         = render 'shared/notifications/button', notification_setting: @notification_setting