The ornamental design for a decoy, as shown and described.
FIG. 1 shows left side and top perspective views of the constituent parts of a first embodiment of a decoy according to the present design, the right side and bottom images being mirror images thereof;
FIG. 2 is an assembled top perspective view of a first embodiment of a decoy according to the present design;
FIG. 3 is an assembled front view of a first embodiment of a decoy according to the present design;
FIG. 4 is an assembled rear view of a first embodiment of a decoy according to the present design;
FIG. 5 is an assembled left side view of a first embodiment of a decoy according to the present design;
FIG. 6 is an assembled right side view of a first embodiment of a decoy according to the present design;
FIG. 7 is an assembled top view of a first embodiment of a decoy according to the present design;
FIG. 8 is an assembled bottom view of a first embodiment of a decoy according to the present design; and,
FIG. 9 is a left side view of a first embodiment of a decoy according to the present design, showing the head/neck of the decoy in various possible degrees of rotation; the elements shown in dashed lines are for illustration purposes only and form no part of the present invention.