The ornamental design for a nestingcontainer, as shown and described.
FIG. 1 is a front isometric view of a nesting container in accordance with the new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a left view thereof; and,
FIG. 7 is a right view thereof.
The broken lines shown in FIGS. 1, 2, 3, 4, and 6 are for the purpose of illustrating portions of the nesting container that form no part of the claimed design.