The ornamental design for a spongeholder, as shown and described.
FIG. 1 is a perspective view of a sponge holder showing our new design;
FIG. 2 is a top view of the sponge holder of FIG. 1;
FIG. 3 is a bottom view of the sponge holder of FIG. 1;
FIG. 4 is a right side view of the sponge holder of FIG. 1;
FIG. 5 is a left side view of the sponge holder of FIG. 1;
FIG. 6 is a rear view of the sponge holder of FIG. 1; and,
FIG. 7 is a front view of the sponge holder of FIG. 1.
The broken lines in the drawings are shown for illustrative purposes only and form no part of the claimed design. In addition, the surface shading illustrated in the drawings is provided merely to highlight the contour of design; it is not intended to be illustrative of texture or gloss.