The ornamental design for a broom, as shown and described.
FIG. 1 is a perspective view of the new design for a broom;
FIG. 2 is a front view thereof, the rear view being a mirror image thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a bottom view thereof;
FIG. 5 is a right side view thereof, the left side view being a mirror image thereof; and,
FIG. 6 is a perspective view thereof showing the mop 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 contour of design; it is not intended to be illustrative of texture or gloss.