The ornamental design which is claimed is shown in solid lines in the figures. The broken lines formed by equal length dashes show unclaimed portions of the lighting device. The dash-dot broken lines show boundaries between claimed and unclaimed portions of the design. The broken lines form no part of the claimed design. The lighting device is shown with symbolic breaks in its height, represented by jagged lines. Lines having a jagged element show that no particular length of the portion is claimed. The appearance of any portion of the lighting device between the jagged lines forms no part of the claimed design.