The ornamental design for a dustpan, as shown and described.
FIG. 1 is a top, front, right perspective view of a dustpan showing a first embodiment of our new design;
FIG. 2 is a top view thereof;
FIG. 3 is a right side view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a top, front, right perspective view of a dustpan showing a second embodiment of our new design;
FIG. 6 is a top view thereof;
FIG. 7 is a right side view thereof; and,
FIG. 8 is a left side view thereof.
The uneven-length broken lines represent unclaimed boundaries of the claimed design. The even-length broken lines showing the remainder of the dustpan are for environmental purposes only and form no part of the claimed design.