The ornamental design for lighting fixture, as shown and described.
FIG. 1 is a front perspective view of a lighting fixture showing a first embodiment of a new design;
FIG. 2 is a back perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a back elevational view thereof;
FIG. 5 is a left elevational view thereof;
FIG. 6 is a right elevational view thereof;
FIG. 7 is a top plan view thereof; and
FIG. 8 is a bottom plan view thereof;
FIG. 9 is a front perspective view of a lighting fixture showing a second embodiment of a new design;
FIG. 10 is a back perspective view thereof;
FIG. 11 is a front elevational view thereof;
FIG. 12 is a back elevational view thereof;
FIG. 13 is a left elevational view thereof;
FIG. 14 is a right elevational view thereof;
FIG. 15 is a top plan view thereof; and,
FIG. 16 is a bottom plan view thereof.
The broken lines extending from the perimeter of the lighting fixtures in FIGS. 5-8 and FIGS. 13-16 represent environment which forms no part of the claimed design. The remaining broken line disclosures in the views represent portions of the lighting fixture that form no part of the claimed design.