The ornamental design for a boxspringwrap, as shown and described.
FIG. 1 is a perspective view of the box spring wrap;
FIG. 2 is a front side view thereof, the rear side view being a mirror image of the front side view;
FIG. 3 is a left side view thereof, the right side view being a mirror image of the left side view; and,
FIG. 4 is a top side view thereof, the bottom side being a mirror image of the top side view.
Broken lines, such as those depicted in FIGS. 1 and 4 as representing the mattress, are for environmental purposes only and form no part of the claimed design.