The ornamental design for a foldablesolarpanel, as shown and described.
FIG. 1 is a perspective view of a foldable solar panel in use condition showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a rear view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines in the drawings are intended to show portions of the panel that are not being claimed, and thus form no part of the claimed design. The dot-dash lines shown in the drawings define the boundary between the claimed design and the non-claimed design.