The ornamental design for a necklace, as shown and described.
FIG. 1 is a front elevation view of a first embodiment of a necklace showing my new design;
FIG. 2 is a front elevation of a second embodiment of the necklace;
FIG. 3 is a perspective view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a side view thereof.
The broken lines in the drawings represent portions of the necklace that form no part of the claimed design. The text and indicia reading “NAME”, which is shown in broken lines, represents environmental subject matter only and forms no part of the claimed design.