We claim the ornamental design for a dishwasher water softener cap, as shown and described.
FIG. 1 is a front perspective view of a dishwasher water softener cap shown in its environment of a dishwasher;
FIG. 2 is a front, right perspective view of the dishwasher water softener cap of FIG. 1;
FIG. 3 is a front elevation view of the dishwasher water softener cap of FIG. 2;
FIG. 4 is a back elevation view of the dishwasher water softener cap of FIG. 2;
FIG. 5 is a right elevation view of the dishwasher water softener cap of FIG. 2;
FIG. 6 is a left elevation view of the dishwasher water softener cap of FIG. 2;
FIG. 7 is a top plan view of the dishwasher water softener cap of FIG. 2; and,
FIG. 8 is a bottom plan view of the dishwasher water softener cap of FIG. 2.
The broken lines in FIGS. 1 and 2 form no part of the claimed design. FIGS. 2-8 show the dishwasher water softener cap enlarged relative to that shown in FIG. 1 with the dishwasher water softener cap in its environment.