message: margin for horizontal row
diff: flex-direction: column;
  }
  +.FormLayoutGroup--vertical > * ~ * {
  + margin-top: 12px;
  + }
  +
  .FormLayoutGroup--horizontal {
  flex-direction: row;
  }
  -.FormLayoutGroup--vertical > * ~ * {
  - margin-top: 12px;
  +.FormLayoutGroup--horizontal > * ~ * {
  + margin-left: 20px;
  }
  