The ornamental design for workout bench, as shown and described.
FIG. 1 is a perspective view of the design of this invention;
FIG. 2 is a top view;
FIG. 3 is a side view;
FIG. 4 is a first end view;
FIG. 5 is a second end view; and,
FIG. 6 is a bottom view.
The broken line showing of portions of a workout bench is for the purpose of illustrating portions of the article that form no part of the claimed design.