The ornamental design for a toolholder, as shown and described.
FIG. 1 is a front elevational view of a tool holder showing my new design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a right elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan; and,
FIG. 6 is an isometric view thereof.
The dashed lines in FIGS. 1 through 6 represent stitching and form part of the claimed design. The broken lines shown in FIG. 6 are for illustrative purposes only and form no part of the claimed design.