The ornamental design for a bottlebrush, as shown and described.
FIG. 1 is a front elevation view of my new design;
FIG. 2 is a rear elevation view;
FIG. 3 is a left elevation view;
FIG. 4 is a right elevation view;
FIG. 5 is a top elevation view;
FIG. 6 is a bottom elevation;
FIG. 7 is a diagonal raised front elevation view; and,
FIG. 8 is a longitudinal cross-section view.
The interior rod shown in broken lines in FIG. 8 is for the purpose of illustrating an interior support feature and forms no part of the claimed design.