HELSINKI—Estonia’s prime minister resigned Wednesday over a corruption scandal involving a key official of his Center Party suspected of accepting a private donation for the party in exchange for a political favor on a real estate deal, prompting new talks on forming a new ruling coalition. The resignation of Prime Minister Juri Ratas, who is also the Center Party’s leader, automatically triggers the resignation of Estonia’s three-party coalition government, but doesn’t automatically mean a new election. Ratas said early Wednesday on his Facebook page that he would step down as “the suspicion expressed by the Public Prosecutor’s Office …. does not mean that someone is definitely guilty but they will inevitably cast a serious shadow over all those involved.” “In such a situation, it seems only right that, by resigning myself, I will give the opportunity to shed light on all the facts and come to clarity,” Ratas wrote on …