The ornamental design for a jacket, as shown and described.
FIG. 1 is a front perspective view of a jacket showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is an opposite side front perspective view thereof; and,
FIG. 4 is an enlarged view of the claimed design in FIG. 2 with environment removed for clarity purposes.
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 depict portions that form no part of the claimed design.