The ornamental design for a necklace, as shown and described.
FIG. 1 is a top front perspective view of a necklace showing my new design, wherein the broken lines shown on the drawing represent portions of the necklace that form no part of the claimed design;
FIG. 2 is an elevational back view of the necklace of FIG. 1;
FIG. 3 is an elevational right edge view of the necklace of FIG. 1;
FIG. 4 is an elevational left edge view of the necklace of FIG. 1;
FIG. 5 is an elevational bottom edge view of the necklace of FIG. 1; and,
FIG. 6 is an elevational top edge view of the necklace of FIG. 1.