The ornamental design for a boot, as shown and described.
FIG. 1 is a side perspective view of a boot showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a side view thereof;
FIG. 5 is an opposite side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The uneven-length broken lines immediately adjacent to the shaded areas define the bounds of the claimed design and form no part thereof. The even-length broken lines within the shaded area represent stitching. The even-length broken lines depicting the remainder of the boot show features that form no part of the claimed design.