The ornamental design for a ringholder, as shown and described.
FIG. 1 is an isometric view of a ring holder.
FIG. 2 is another isometric view of the ring holder of FIG. 1.
FIG. 3 is a top plan view of the ring holder of FIG. 1.
FIG. 4 is a bottom view of the ring holder of FIG. 1.
FIG. 5 is front view of the ring holder of FIG. 1.
FIG. 6 a rear view of the ring holder of FIG. 1.
FIG. 7 is a left side view of the ring holder of FIG. 1; and,
FIG. 8 is a right side view of the ring holder of FIG. 1.
Portions of FIGS. 1 through 8 are shown in broken lines and dash-dot-dash boundary lines illustrating portions of the article that form no part of the claimed design.