By Parisa Hafezi DUBAI (Reuters) -An attack on a Shi’ite Muslim shrine in the Iranian city of Shiraz killed 13 people on Wednesday, authorities said, and President Ebrahim Raisi vowed that the shooting by suspected Sunni Muslim militants would not go unanswered. The killing of Shi’ite pilgrims praying at the Shah Cheragh shrine in Shiraz increased tension in a country reeling from weeks of protests sparked by the killing in custody of Kurdish woman Mahsa Amini. Security forces clashed with protesters marking 40 days since death of the 22-year-old’s death. Interior Minister Ahmad Vahidi said ma…