The ornamental design for a tailgate, as shown and described.
FIG. 1 is a front left elevated perspective view of a tailgate according to the present invention.
FIG. 2 is a front left perspective view of the tailgate shown in FIG. 1.
FIG. 3 is a rear right elevated perspective view thereof.
FIG. 4 is a rear right perspective view thereof.
FIG. 5 is a front view thereof.
FIG. 6 is a rear view thereof.
FIG. 7 is a left side view thereof.
FIG. 8 is a right side view thereof.
FIG. 9 is a top view thereof.
FIG. 10 is a bottom view thereof; and,
FIG. 11 is another front left perspective view thereof, but mounted on a vehicle to show environmental structure, the vehicle being unclaimed and shown in broken lines.