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 right, front perspective view of the jacket, shown in a first alternate position of use;
FIG. 3 is a front view of the jacket, shown in a second alternate position of use;
FIG. 4 is a right side view of the jacket, shown in a third alternate position of use;
FIG. 5 is a left side view of the jacket of FIG. 4; and,
FIG. 6 is a back view of the jacket of FIG. 4.
The even-length broken lines represent parts of the jacket that 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.