FIG. 1 is a front perspective view of a showerhead showing our new design; FIG. 2 is a rear perspective view thereof; FIG. 3 is a front face view thereof; FIG. 4 is a rear view thereof; FIG. 5 is a first side view thereof; and, FIG. 6 is a second side view thereof. The broken line showing is included for the purpose of illustrating and forms no part of the claimed design.