The ornamental design for a boot, as shown and described.
FIG. 1 is a front, top and right side perspective view of a boot showing the design;
FIG. 2 is a right side elevation thereof;
FIG. 3 is a left side elevation view thereof;
FIG. 4 is a front elevation view thereof;
FIG. 5 is a rear elevation view thereof; and
FIG. 6 is top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The broken line showing is of environmental material and forms no part of the claimed design. The varying density of stippling over the surface of the boot in all figures is used to illustrate light and shadow only, and no specific colors, materials, or finishes are hereby claimed.