Paramount Skydance boss David Ellison has bid $24 a share for Warner Bros. Discovery – a mega-deal worth$57 billion that was nevertheless rejected as takeover negotiations between the media giants heat up, The Post has learned.The latest back and forth – which has played out only in recent days – marks the third straight time Ellison has been rebuffed as WBD’s wily CEO David Zaslav shops the company to a number of large media and tech outfits, sources said. News of the spurned $24-a-share bid hasn’t previo ...