The ornamental design for a divertervalve, as shown and described.
FIG. 1 is a perspective view of a diverter valve showing our new design;
FIG. 2 is a first end view thereof;
FIG. 3 is a second end view thereof;
FIG. 4 is a first side view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a third side view thereof; and,
FIG. 7 is a fourth side view thereof.
The broken line showing of a rear attachment are included for the purpose of illustrating a portion of the diverter valve that forms no part of the claimed design.