The ornamental design for a ringholder, as shown and described.
FIG. 1 is a perspective view of a ring holder.
FIG. 2 is an alternative perspective view thereof.
FIG. 3 is a front elevational view thereof.
FIG. 4 is a rear elevational view thereof.
FIG. 5 is a right side elevational view thereof.
FIG. 6 is a left side elevational view thereof.
FIG. 7 is a top plan view thereof.
FIG. 8 is a bottom plan view thereof; and,
FIG. 9 illustrates an example environment in which the ring holder may be used.
Any broken lines (e.g., dash lines, dot lines, dash-dot-dash-dot lines) of FIGS. 1-8 illustrate portions of the ring holder that form no part of the claimed design. The broken lines of FIG. 9 illustrate environmental matter and form no part of the claimed design.