FIG. 1 is a top view of a light bulb showing my new design; FIG. 2 is a first side view thereof; FIG. 3 is a second side view thereof; FIG. 4 is a third side view thereof; FIG. 5 is a fourth side view thereof; and, FIG. 6 is a bottom view thereof. The broken lines in the figures are for illustrative purposes only and form no part of the claimed design.