The ornamental design for a skateboot, as shown and described.
FIG. 1 is a perspective view taken from a front, top, left side of a skate boot according to a first embodiment of my design;
FIG. 2 is a left side elevation view thereof;
FIG. 3 is a rear elevation view thereof; and,
FIG. 4 is a right side elevation view thereof.
Throughout the Figures, where shown: (i) the dotted lines showing the remainder of the skate boot are for illustrative purposes only and form no part of the claimed design; (ii) the unshaded surfaces form no part of the claimed design; and (iii) the dotted/dashed lines illustrate unclaimed boundaries of surfaces claimed as part of the design.