The ornamental design for a displayshelf, as shown and described.
FIG. 1 is a perspective view of a display shelf with environment showing our new design;
FIG. 2 is a perspective view thereof without environment;
FIG. 3 is a front view thereof;
FIG. 4 is right side view thereof, the left side view being a mirror image;
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The broken lines shown in the drawings are included for purposes of illustrating environment or portions of the display shelf and form no part of the claimed design.