The ornamental design for a lightingfixture, as shown and described.
FIG. 1 is a top perspective view of a new lighting fixture;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a left elevational view thereof;
FIG. 5 is a right elevational view thereof;
FIG. 6 is a from elevational view thereof;
FIG. 7 is a back elevational view thereof; and,
FIG. 8 is a top plan view thereof.
The horizontal broken line depicted at the top of the fixture on FIGS. 4 through 7 represents environmental structure to which the fixture is mounted, which forms no part of the claimed design. The remaining broken line disclosures in the views represent portions of the lighting fixture which form no part of the claimed design.