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 left side view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a front view thereof; and,
FIG. 5 is an opposite side front perspective view thereof.
The broken lines immediately adjacent to the shaded area define the bounds of the claimed design and form no part thereof. The broken lines depicting the remainder of the jacket form no part of the claimed design.