The ornamental design for a necklace, as shown and described.
FIG. 1 is a perspective view of the necklace of the present design;
FIG. 2 is a front view of the necklace shown in FIG. 1;
FIG. 3 is a rear view of the necklace shown in FIG. 1;
FIG. 4 is a left side view of the necklace of FIG. 1;
FIG. 5 is a top view of the necklace of FIG. 1; and,
FIG. 6 is a bottom view of the necklace of FIG. 1.
The broken lines in the drawings illustrate portions of the necklace that form no part of the claimed design. The other broken lines showing a beaded chain merely represent environmental subject matter and form no part of the claimed design.