The ornamental design for a lightingfixture, as shown and described.
The single FIGURE is a perspective front view of a lighting fixture showing the new design, for which a perspective view rotated 72° with respect thereto would be identical, for which a perspective view rotated 144° with respect thereto would be identical, for which a perspective view rotated 216° with respect thereto would be identical, and for which a perspective view rotated 288° with respect thereto would be identical.
The broken lines form no part of the claimed design and either represent the bounds of the claimed design (e.g., the broken lines immediately adjacent shaded areas and the broken lines immediately adjacent portions of the design represented in solid lines) or are directed to environment (e.g., different portions of the shades) and are for illustrative purposes only.