The ornamental design for a skateboarddeck, as shown and described.
FIG. 1 is a top perspective view of the skateboard deck.
FIG. 2 is a bottom perspective view of the skateboard deck.
FIG. 3 is a front elevation view of the skateboard deck.
FIG. 4 is a back elevation view of the skateboard deck.
FIG. 5 is a left side elevation view of the skateboard deck.
FIG. 6 is a right side elevation view of the skateboard deck.
FIG. 7 is a top plan view of the skateboard deck; and,
FIG. 8 is a bottom plan view of the skateboard deck.
The evenly-dashed broken lines in the drawings illustrate portions of the skateboard deck that form no part of the claimed design. The dashed-dot broken lines in the drawings depict the boundary between claimed and unclaimed subject matter and form no part of the claimed design.