The ornamental design for belt, as shown and described.
FIG. 1 is a perspective view of a belt showing my new design;
FIG. 2 is a front elevational view thereof; the rear side being substantially a mirror image;
FIG. 3 is a top plan view thereof; the bottom side being substantially a mirror image; and,
FIG. 4 is a right side elevational view thereof; and the left side being substantially a mirror image.
The belt is shown with a symbolic break in its length. The appearance of any portion of the article between the break lines forms no part of the claimed design.