The ornamental design for a vanity, as shown and described.
FIG. 1 is a front perspective view of a vanity showing my new design;
FIG. 2 is a front view of the vanity shown in FIG. 1;
FIG. 3 is a right side view of the vanity shown in FIG. 1 (with the left side view being a mirror image); and,
FIG. 4 is a top view of the vanity shown in FIG. 1.
The broken line showing of the faucet holes, drain hole, spillover hole, sink, countertop, and handles is for illustrative purposes only and forms no part of the claimed design. The back of the vanity is plain and unornamented.