The ornamental design for a packingcase, as shown and described.
FIG. 1 is a top plan view of a packing case showing my new design;
FIG. 2 is a bottom plan view of the packing case of FIG. 1;
FIG. 3 is a front elevation view of the packing case of FIG. 1;
FIG. 4 is a rear elevation view of the packing case of FIG. 1;
FIG. 5 is a top, front, right perspective view of the packing case of FIG. 1;
FIG. 6 is a top, right perspective view of the packing case of FIG. 1; and,
FIG. 7 is a top, rear perspective view of the packing case of FIG. 1.
All broken lines in all figures are included for the purpose of illustrating environment and unclaimed features of the design and form not part of the claimed design.