The ornamental design for a container, as shown and described.
FIG. 1 is a front perspective view of the new design;
FIG. 2 is a side plan view thereof, wherein an identical view is depicted when the design is rotated about its vertical axis ninety degrees to the right;
FIG. 3 is a front plan view thereof, wherein an identical view is depicted when the design is rotated about its vertical axis ninety degrees to the left;