The ornamental design for a comb, as shown and described.
FIG. 1 is a left side view of a comb showing my new design.
FIG. 2 is a right side view of the comb of FIG. 1.
FIG. 3 is a back view of the comb of FIG. 1.
FIG. 4 is a front view of the comb of FIG. 1.
FIG. 5 is a top view of the comb of FIG. 1.
FIG. 6 is a bottom view of the comb of FIG. 1; and,
FIG. 7 is a top perspective view of the comb of FIG. 1.
The broken lines illustrating portions of the comb form no part of the claimed design. The long dash-dot lines in the figures represent an unclaimed boundary line and form no part of the claimed design.