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 top view thereof;
FIG. 4 is a left side view thereof, the right side view being a mirror image thereof;
FIG. 5 is a rear view thereof; and,
FIG. 6 is a bottom view thereof.
The dashed broken lines in FIGS. 1-6 show unclaimed portions of the lighting device. The dashed-dotted broken lines in FIGS. 1-3, 5, and 6 show unclaimed boundaries of the claimed design. The oblique line shading in FIGS. 1 and 2 shows a translucent or transparent material.