We claim the ornamental design for a lighting device, as shown and described.
FIG. 1 is a front, top, left perspective view of the claimed design;
FIG. 2 is a front, bottom, left perspective view of the claimed design;
FIG. 3 is a rear, top, left perspective view of the claimed design;
FIG. 4 is a rear, bottom, left perspective view of the claimed design;
FIG. 5 is a front view of the claimed design;
FIG. 6 is a rear view of the claimed design;
FIG. 7 is a right side view of the claimed design;
FIG. 8 is a left side view of the claimed design;
FIG. 9 is a top view of the claimed design; and,
FIG. 10 is a bottom view of the claimed design.
The ornamental design which is claimed is shown in solid lines in the figures. The equal length dashed lines show portions of the article and form no part of the claimed design. The dash-dot-dash lines show the bounds of the claim and form no part of the claimed design.