The ornamental design for a lightfixture, as shown and described.
FIG. 1 is a top perspective view of a light fixture in accordance with my design;
FIG. 2 is a top plan view of a light fixture in accordance with my design;
FIG. 3 is a bottom plan view of a light fixture in accordance with my design; and,
FIG. 4 is a side elevation view of a light fixture in accordance with my design, the sides opposite and adjacent being identical in appearance to that shown.
The broken line disclosure in the views is understood to represent unclaimed portions of the article in which the claimed design is embodied, but which form no part of the claimed design.