The ornamental design for a belt, as shown and described.
FIG. 1 is a top-left, front perspective view of the belt;
FIG. 2 is a top plan view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a bottom plan view thereof;
FIG. 5 is a right side elevational view thereof;
FIG. 6 is a left side elevational view thereof; and,
FIG. 7 is a front perspective view of the belt as would be worn.
The strap portions of the belt shown in broken lines in FIGS. 1-7 do not form a part of the design. All other broken lines in FIG. 7 depict environment, which forms no part of the claimed design.