N°3685 Compile SCSS files as a compressed CSS file and fix SCSS copyright comment so that they don't end up in compiled CSS

css/backoffice/pages/_csv-import.scss

@@ -1,7 +1,8 @@
-/*!
+/*
  * @copyright   Copyright (C) 2010-2021 Combodo SARL
  * @license     http://opensource.org/licenses/AGPL-3.0
  */
+
 #tabs1-import .ibo-field--label {
   max-width: 50%;
 }