The ornamental design for an inkcartridge, as shown and described.
FIG. 1 is a rear, right-side perspective view of an ink cartridge;
FIG. 2 is a front view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a right-side view thereof;
FIG. 5 is a left-side view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a front, left-side perspective view thereof.
The broken lines depict unclaimed portions of the ink cartridge and form no part of the claimed design. The dot-dash chain lines depict a boundary of the claimed subject matter and form no part of the claimed design.