Calgary Mayor Naheed Nenshi won’t be running in the municipal election in the fall. Nenshi, the first Muslim mayor of a big Canadian city when he was elected in October 2010, made the announcement Tuesday on social media. The 49-year-old, who has a master’s degree from Harvard University, has served as mayor of Calgary for three terms. He said leading the city has been the honour of his life. “It was a tough decision to make but, ultimately, I think the right decision for me and I really hope the right decision for Calgary,” Nenshi said on a Facebook livestream. He added that he’s not going anywhere and his family is fine, but it’s time to make room in the job for someone else. Nenshi said he sought a lot of advice on the matter. But the hardest conversation he had was with himself. “Is it irresponsible at this moment …