The ornamental design for a lightfixture, as shown and described.
FIG. 1 is a perspective view of a light fixture embodying the new design;
FIG. 2 is a front view thereof;
FIG. 3 is a left-side view thereof;
FIG. 4 is a right-side view thereof;
FIG. 5 is a top view thereof; and,
FIG. 6 is bottom view thereof.
The broken line showing in the drawings is included for the purpose of illustrating portions of the light fixture and forms no part of the claimed design.