The ornamental design for a lightingfixture, as shown and described.
FIG. 1 is a front perspective view of a new lighting fixture;
FIG. 2 is a back perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a left elevational view thereof;
FIG. 5 is a right elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a back elevational view thereof.
The broken line disclosure in the views represents portions of the lighting fixture that form no part of the claimed design. The broken-line extending out beyond the perimeter of the back surface of the fixture in FIGS. 4-7 is intended to demonstrate environment only and forms no part of the claimed design.