I claim the ornamental design for a lighting fixture, as shown and described.
FIG. 1 is a left side elevational view of the lighting fixture.
FIG. 2 is a front elevational view of the lighting fixture.
FIG. 3 is a rear elevational view of the lighting fixture.
FIG. 4 is a right side elevational view of the lighting fixture.
FIG. 5 is a top plan view of the lighting fixture; and,
FIG. 6 is an isometric view of the lighting fixture.
FIGS. 1–6 are views of a lighting fixture. The broken lines represent the bounds of the claimed design; the broken lines form no part of the claimed design.