An air of sadness hung about Le Petit Paris Wednesday after the owners announced they will close late this month. The boutique and Parisian cafe has brought a bit of France to Midtown for the last five years, but it's been struggling for at least two. Owners Tassina Placencia and her husband Ruben plan to close the family business at 1221 19th St. on Sept. 26. The economy and fewer customers — including state workers making less money because they're furloughed many Fridays — have contributed to the problem, Tassina Placencia said Wednesday afternoon. "It's not what it was," she said during a break from serving customers who lined up at the counter. "No one's buying coffee anymore. You