The ornamental design for a sidingsplicejoint, as shown and described.
FIG. 1 is a perspective view of a siding splice joint;
FIG. 2 is a front elevation view thereof, which is a mirror image to the rear elevation view;
FIG. 3 is a top plan view thereof;
FIG. 4 is a bottom plan view thereof; and,
FIG. 5 is a left side elevation view thereof, which is a mirror image of the right side elevation view.
The broken lines shown in the figures that are immediately adjacent to the shaded areas and define unshaded regions represent the bounds of the claim. The broken lines form no part of the claimed design.