The ornamental design for a spreader, as shown and described.
FIG. 1 is a rear and side perspective view of the spreader, showing my new design;
FIG. 2 is a right side view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a rear elevational view thereof; and,
FIG. 6 is a top plan view thereof.
The broken line showing of surface and mechanical features is included for the purpose of illustrating portions of the spreader and forms no part of the claimed design.