The ornamental design for an inkcartridge, as shown and described.
FIG. 1 is a top front perspective view of an ink cartridge showing my new design;
FIG. 2 is a bottom front perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a right side view thereof; and,
FIG. 8 is a left side view thereof.
The broken lines are shown for illustrative purposes only and form no part of the claimed design. The dot-dashed lines denote the boundary of the claim, and form no part of the claimed design.