The ornamental design for a dustbasket, as shown and described.
FIG. 1 is a front elevational view of a dust basket showing my new design;
FIG. 2 is a top plan view;
FIG. 3 is a right side elevational view; and
FIG. 4 is a bottom plan view thereof.
The rear elevational view is the mirror image of the front elevational
view; and the left side elevational view is the mirror image of the right
side elevational view.