The ornamental design for a petsuspender, as shown and described.
FIG. 1 is a top perspective view of a pet suspender in accordance with the new design;
FIG. 2 is a top view thereof;
FIG. 3 is a bottom view thereof;
FIG. 4 is a front view thereof;
FIG. 5 is a rear view thereof;
FIG. 6 is a left side view thereof; and,
FIG. 7 is a right view thereof.
The equal-length broken lines that show fasteners, hardware and suspender pads in the drawings depict environmental matter and form no part of the claimed design. The broken lines on the suspender straps depict stitching that forms part of the claimed design.