The ornamental design for a toolholder, as shown and described.
FIG. 1 is an upper perspective view of a tool holder showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a side view thereof;
FIG. 5 is an opposite side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof;
FIG. 8 is a first lower perspective view thereof; and,
FIG. 9 is a second lower perspective view thereof.
The circular shapes illustrated in broken lines in FIGS. 1, 2 and 6 depict unclaimed portions of the tool holder that form no part of the claimed design.