The ornamental design for a lightingfixture, as shown and described.
FIG. 1 is a bottom perspective view of a lighting fixture depicting a new design;
FIG. 2 is a top 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.
The break lines shown in the drawings indicate that the appearance of any portion of the article between the break lines forms no part of the claimed design. The broken line disclosures in the views represent portions of the lighting fixture that form no part of the claimed design.