The ornamental design for a brushholder, as shown and described.
FIG. 1 is an exploded left side perspective view of a brush holder in accordance with my invention;
FIG. 2 is a perspective view of a constituent part of the brush holder in FIG. 1, shown without the other parts of the brush holder for convenience of illustration.
FIG. 3 is a left side perspective view of the brush holder shown in FIG. 1; and,
FIG. 4 is a front side elevation view of the brush holder shown in FIG. 1.