The ornamental design for a scoreboard, as shown and described.
FIG. 1 is a front top right perspective view of a scoreboard within the environment of attachment with a fence. The broken lines showing the fence and symbols are for the purpose of illustrating the environmental structure and form no part of the claimed design;
FIG. 2 is a right side elevation view of a scoreboard. The broken lines showing symbols are for the purpose of illustrating the environmental structure and form no part of the claimed design;
FIG. 3 is a left side elevation view thereof. The broken lines showing symbols are for the purpose of illustrating the environmental structure and form no part of the claimed design;