The ornamental design for a lightingdevice, as shown and described.
FIG. 1 is a front perspective view of a lighting device showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a left side view thereof, the right side view being a mirror image thereof;
FIG. 4 is a top view thereof; and,
FIG. 5 is bottom view thereof.
The broken lines in FIGS. 1-5 show unclaimed portions of the lighting device. The rear view is omitted and forms no part of the claimed design. The oblique line shading in FIGS. 1, 2, and 5 shows translucent or transparent materials.