The ornamental design for the boot, as shown and described.
FIG. 1 is an isometric view of a boot showing the new design.
FIG. 2 is a front elevational view thereof.
FIG. 3 is a rear elevational view thereof.
FIG. 4 is a right-side elevational view thereof.
FIG. 5 is a left-side elevational view thereof.
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The dashed lines in the drawings represent portions of the boot that do not form any part of the claimed design. Further, the dash-dot-dash lines immediately adjacent to the solid line portions of the boot form the boundary of the design and form no part of the claimed design.