FIG. 1 is a front, left side perspective view of a cart showing my design, and the front, right side perspective view is a mirror image. FIG. 2 is a front view of the cart of FIG. 1; FIG. 3 is a left side elevational view of the cart of FIG. 1 and the front right side elevational view is a mirror image; FIG. 4 is a rear elevational view of the cart of FIG. 1; FIG. 5 is a top plan view of the cart of FIG. 1; and, FIG. 6 is a bottom plan view of the cart of FIG. 1. The features shown in dotted line do not form part of the claimed design.