The ornamental design for a lightingfixture, as shown and described.
FIG. 1 is a front perspective view of the lighting fixture showing our new design;
FIG. 2 is a top plan view thereof, with the bottom plan view being the same; and,
FIG. 3 is a left side elevational view thereof, with the right side elevational view, the front elevational view, and the rear elevational view all being the same.
The broken lines in FIG. 1-FIG. 3 are for the purposes of illustrating environment only and form no part of the claimed design.