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 illustrate unclaimed portions of the boot. The dash dot dash lines immediately adjacent to the solid line portions of the boot define the bounds of the claimed design and form no part thereof.