The ornamental design for a boot, as shown and described.
FIG. 1 illustrates a right side perspective view of a boot according to the present disclosure;
FIG. 2 illustrates a left side perspective view thereof;
FIG. 3 illustrates a back side perspective view thereof;
FIG. 4 illustrates a front side perspective view thereof;
FIG. 5 illustrates a top perspective view thereof;
FIG. 6 illustrates a bottom perspective view thereof; and,
FIG. 7 illustrates another right side perspective view thereof.
The broken lines showing the pull tabs depict parts of the boot that form no part of the claimed design; while the remaining broken lines depict stitching that form part of the claimed design.