message: ModalPageHeader: increaase content flex-grow on iOS viewports >= 320px
diff: justify-content: center;
  }
  +@media (min-width: 320px) {
  + .ModalPageHeader--ios .ModalPageHeader__content {
  + flex-grow: 3;
  + }
  +}
  +
  .ModalPageHeader--ios .ModalPageHeader__right {
  flex-grow: 1;
  flex-basis: 0;
  