The ornamental design for a set-top box, as shown and described.
FIG. 1 is a top perspective view of a set-top box according to an aspect of the present disclosure;
FIG. 2 is a bottom perspective view of the set-top box of FIG. 1;
FIG. 3 is a top view of the set-top box of FIG. 1;
FIG. 4 is a bottom view of the set-top box of FIG. 1;
FIG. 5 is a front view of the set-top box of FIG. 1;
FIG. 6 is a rear view of the set-top box of FIG. 1;
FIG. 7 is a left side view of the set-top box of FIG. 1; and,
FIG. 8 is a right side view of the set-top box of FIG. 1.
The broken line portion “- - -” of the drawings is included to show unclaimed subject matter only for the purpose of illustrating environment and forms no part of the claimed design.