react-share 2.0 shipped function components with defaultProps (CreatedButton,
Icon) -> React-19-blocking warnings on fire-detail pages. v5 is React-18-safe
and drops them. Removed the GooglePlusShareButton/Icon (Google+ is dead;
removed from react-share in v4+); the other 6 buttons (Facebook, Twitter,
Telegram, WhatsApp, Reddit, Email) are API-compatible. Browser-verified 6
buttons render, no defaultProps warnings. REST smoke byte-identical.