The ornamental design for a container, as shown and described.
FIG. 1 is a perspective view of a container, showing the new design;
FIG. 2 is a first side view thereof;
FIG. 3 is a second side view thereof;
FIG. 4 is a top view thereof; and,
FIG. 5 is a bottom view thereof.
The broken lines shown in the figures are included for the purpose of illustrating portions of the container and do not form part of the claimed design.