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.