The ornamental design for luggage, as shown and described.
FIG. 1 is a perspective view of an embodiment of the luggage.
FIG. 2 is front view of the luggage of FIG. 1.
FIG. 3 is a rear view of the luggage of FIG. 1.
FIG. 4 is left side view of the luggage of FIG. 1.
FIG. 5 is right side view of the luggage of FIG. 1.
FIG. 6 is a top view of the luggage of FIG. 1; and,
FIG. 7 is a bottom view of the luggage of FIG. 1.
Elements of the design which are depicted entirely in broken lines, including zippers and stitching, are illustrative of environment and form no part of the claimed design.