San Francisco’s booming real estate market, which has led to the displacement of nonprofits, artists and longtime residents, is now set to oust one of Union Square’s oldest and most storied retailers. Shreve & Co., the high-end jeweler that moved into 200 Post St. in March 1906, a month before the earthquake and fire, has been unable to renew its lease, said Lane Schiffman, the company’s managing partner and co-owner. Schiffman’s, the Greensboro, N.C., jewelry store chain that bought Shreve & Co.