The ornamental design for a lightfixture, as shown and described.
FIG. 1 is a perspective view of a light fixture in accordance with my new design;
FIG. 2 is a top plan view of the light fixture in accordance with my new design;
FIG. 3 is a bottom plan view of the light fixture in accordance with my new design;
FIG. 4 is a left-side elevation view of the light fixture in accordance with my new design, the right-side elevation view being a mirror image of that shown; and,
FIG. 5 is a front elevation view of the light fixture in accordance with my new design.
The broken lines shown on the drawings depict portions of the light fixture that form no part of the claimed design.