Enable stylelint check for index.css in GitLab CI pipeline

Proposed resolution

• Remove /* stylelint-disable */ in cloud/modules/cloud_dashboard/cloud_dashboard/src/index.css
  

  /* stylelint-disable */
  /* csslint ignore:start */
  .navbar-default .navbar .navbar-collapse nav ul.navbar-nav li div.menu {
    position: relative;
    display: block;
    padding: 10px 44px 10px 10px;
    cursor: pointer;
    -webkit-transition: all 0.3s ease-in-out;
    -moz-transition: all 0.3s ease-in-out;
    -ms-transition: all 0.3s ease-in-out;
    -o-transition: all 0.3s ease-in-out;
    transition: all 0.3s ease-in-out;
    white-space: inherit;
    word-break: break-all;
    color: rgba(255, 255, 255, 0.87);
    font-size: 16px;
    font-weight: 500;
    line-height: 21px;
  }
  
  ... (snip) ...
  
  /* csslint ignore:end */