The ornamental design for a containercap, as shown and described.
FIG. 1 is an exploded top, front, and right side perspective view of a container cap showing our new design;
FIG. 2 is a front view of the container cap;
FIG. 3 is a side view of the container cap;
FIG. 4 is a top view of the container cap; and,
FIG. 5 is a bottom view of the container cap.
The broken lines illustrate environmental structure which form no part of the claimed design. The dot-dash-dot lines shown in FIGS. 1-4 represent the boundary of the claim.