The ornamental design of a showerhead, as shown and described.
FIG. 1 is a front elevational view of a showerhead according to the present invention; and,
FIG. 2 is a left side elevational view of the showerhead of FIG. 1, the right side, top and bottom views being identical thereto.
The rear surface is unornamented.
The dashed lines illustrate environment that does not form a part of the present invention, and no claim is made to the material illustrated with dashed lines.