I claim the ornamental design for a faucet, as shown and described.
FIG. 1 is a top plan view of a faucet showing my new design with the phantom lines depicting environmental structure and forming no part of the claimed design;
FIG. 2 is a front elevational view thereof with the phantom lines depicting environmental structure and forming no part of the claimed design; and,
FIG. 3 is a left side elevational view thereof with the phantom lines depicting environmental structure and forming no part of the claimed design, the right side being a mirror image.