The ornamental design for a hairbrush, as shown and described.
The patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawing(s) will be provided by the Office upon request and payment of the necessary fee.
1. Hair brush
1.1: Front
1.2: Right
1.3: Back
1.4: Left
1.5: Perspective
1.6: Bottom
The parts indicated with dotted lines are not part of the claimed design.