Artificial intelligence startup Spellbook raised $50 million in a funding round led by Khosla Ventures managing partner Keith Rabois — making the firm the latest venture player to bankroll AI companies tackling the legal industry. Valued at $350 million, the Toronto-based startup helps speed the writing of contracts. It’s part of a rush of AI firms, including Harvey and Eve, betting that AI technology will remake the way law firms do business. Threshold Ventures, existing investor Inovia Capital...