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 the light fixture in accordance with my design;
FIG. 3 is a bottom plan view of the light fixture in accordance with my design; and,
FIG. 4 is a side elevation view of the light fixture in accordance with my design, the opposite view being a mirror image of that shown except for the position of the cord.
The broken line disclosure of a portion of a power cord in the views is for illustrative purposes only and forms no part of the claimed design.