message: refactor: form use css var
diff: -@import '@hi-ui/core-css/index.scss';
  +@import '../../core-css/index.scss';
  .hi-form {
  max-width: 100%;
  legend {
  margin: 0 0 16px;
  - color: $gray-darker;
  + color: use-color('gray-80');
  }
  &--inline {
  box-sizing: border-box;
  margin-top: 0;
  margin-bottom: 24px;
  - font-size: 16px;
  - font-weight: 400;
  + font-size: $font-size-large;
  + font-weight: $font-weight-normal;
  }
  &--label--left {
  flex-shrink: 0;
  box-sizing: border-box;
  vertical-align: top;
  - color: $gray-darker;
  + color: use-color('gray-80');
  overflow-wrap: break-word;
  }
  