The ornamental design for a jacket, as shown and described.
FIG. 1 is a right, front perspective view of a jacket according to the present design;
FIG. 2 is a front view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof; and,
FIG. 5 is a back view thereof.
The even-length broken lines shown in the drawings are directed to environment and form no part of the claimed design.
The long and short broken lines represent the unclaimed boundaries of the claim that do not exist in reality in the article and that form no part of the claim.