message: fix: lighten CSS border for data preview table
  this has been bugging me
diff: @import '../../../stylesheets/less/variables.less';
  .ReactVirtualized__Grid__innerScrollContainer {
  - border: 1px solid;
  + border: 1px solid @gray-light;
  }
  .ReactVirtualized__Table__headerRow {
  font-weight: @font-weight-bold;
  