The ornamental design for a faucet, as shown and described.
FIG. 1 is a front perspective view of a faucet showing my new design;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a back view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken line showing of the spout opening and the bottom circular opening of the base represents unclaimed subject matter and forms no part of the claimed design.