CHICAGO — Mayor Brandon Johnson preempted an outcry from migrants and their supporters Monday, announcing he would not enforce a looming Thursday deadline to start kicking recent arrivals out of city-run shelters. On the eve of a Chicago City Council hearing called to probe conditions at the city’s migrant landing zone and shelters and days before thousands were scheduled to be evicted from the shelters, Johnson said that move would be put off again. “We have made the decision to extend the shelter stay policy based on original exit dates from mid-January through the end of March,” Johnson sai…