Chicago — Aritzia, a women’s fashion boutique retailer based in Vancouver, plans to open a flagship store on Chicago’s Magnificent Mile, bucking a trend of retailers leaving the famous stretch of North Michigan Avenue. The Magnificent Mile spans 13 city blocks in downtown Chicago and houses 460 stores, 275 restaurants and 60 hotels. The retailer, which sells apparel under brands such as Wilfred, Babaton and TNA, will occupy a 46,000-square-foot space at 555 N. Michigan Ave. in 2023. The location formerly housed Gap’s three-story flagship store before the retailer closed …