Bill Cosby’s Manhattan townhouse is back — and cheaper. Weeks after a California jury ordered him to pay nearly $60 million to a woman who alleges he drugged and assaulted her as a teenager in 1972, Cosby has quietly cut the price of his Manhattan townhouse by more than $750,000, The Post has learned.  The Upper East Side dwelling originally hit the market last April for $6.99 million, amid a deepening foreclosure crisis that ensnared two of the Cosby family’s Manhattan properties