The ornamental design for a jacket, as shown and described.
FIG. 1 is a perspective view of a jacket showing our new design in an in-use configuration;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof; and,
FIG. 6 is a top view thereof.
The broken lines immediately adjacent to the shaded area represent unclaimed boundaries of the design. The lighter and darker areas of stippled shading represent contrasted surfaces and do not represent any particular color, material, texture or finish. The broken lines showing the remainder of the jacket are for environmental purposes only and form no part of the claimed design.