The ornamental design for a faucet, as shown and described.
FIG. 1 is a front and left side view of a faucet showing our new design;
FIG. 2 is a left side elevational view thereof shown with the spray head in a pulled out position, the right side elevational view being a mirror image the side view shown;
FIG. 3 is an enlarged view of the upper portion thereof showing the handle in a raised position; and,