message: WriteBarIcon: simplify css assignments
diff: background: none;
  border: 0;
  position: relative;
  - color: var(--writebar_icon);
  + color: var(--icon_secondary);
  height: 52px;
  width: 44px;
  cursor: pointer;
  border-radius: 50%;
  }
  -.WriteBarIcon--send:not(.WriteBarIcon--disabled) {
  +.WriteBarIcon--send,
  +.WriteBarIcon--done {
  color: var(--accent);
  }
  color: var(--writebar_icon);
  }
  +.WriteBarIcon--ios.WriteBarIcon--send:not(:disabled) {
  + color: var(--accent);
  +}
  +
  .WriteBarIcon--ios.WriteBarIcon--send,
  .WriteBarIcon--ios.WriteBarIcon--done {
  width: 48px;
  .WriteBarIcon--ios.WriteBarIcon--done:last-child {
  margin-right: -4px;
  }
  -
  -/**
  - * Android + vkcom
  - */
  -
  -.WriteBarIcon--android,
  -.WriteBarIcon--vkcom {
  - color: var(--icon_secondary);
  -}
  -
  -.WriteBarIcon--android.WriteBarIcon--send,
  -.WriteBarIcon--vkcom.WriteBarIcon--send,
  -.WriteBarIcon--android.WriteBarIcon--done,
  -.WriteBarIcon--vkcom.WriteBarIcon--done {
  - color: var(--accent);
  -}
  