The ornamental design for a jacket, as shown and described.
FIG. 1 is a front view of a jacket according to a first embodiment of the design;
FIG. 2 is a rear view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a rear view of a jacket according to a second embodiment of the design, the front and left side views being the same as FIGS. 1 and 4, respectively; and,
FIG. 6 is a right side view thereof.
The fine broken lines shown in the drawings represent stitching and are part of the claimed design. The symbol depicted in FIGS. 5 and 6 forming part of the claimed design is a registered trademark of Lululemon Athletica Canada Inc.