The ornamental design for a dustpan, as shown and described.
FIG. 1 is a front perspective view of the new design for a dustpan;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a rear view thereof;
FIG. 7 is a right side view thereof;
FIG. 8 is a left side view thereof; and,
FIG. 9 is a perspective view thereof showing the dustpan with a long handle.
The broken lines in the drawings are shown for illustrative purposes only and form no part of the claimed design. In addition, the surface shading illustrated in the drawings is provided merely to highlight the contour of design; it is not intended to be illustrative of texture or gloss.