The ornamental design for a jacket, as shown and described.
FIG. 1 is a front perspective view of a jacket showing our new design;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a side view thereof;
FIG. 6 is a second side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines immediately adjacent to the shaded area represent unclaimed boundaries of the design. The unshaded regions demarcated by broken lines, represent unclaimed portions of the jacket and form no part of the claimed design.