We claim the ornamental design for a vanity top, as shown and described.
FIG. 1 is a right front side perspective view of the vanity top; and
FIG. 2 is a top side view of the design embodiment shown in FIG. 1;
FIG. 3 is a front side view of the vanity top; and,
FIG. 4 is a side view of the vanity top.
The subject matter shown in dashed lines, and any surfaces of the design not shown, including interior surfaces, form no part of the claimed invention.