The ornamental design of a watersofteningdevice, as shown and described.
FIG. 1 is a front elevation view of a water softening device, showing our new design;
FIG. 2 is a rear elevation view thereof;
FIG. 3 is a left side elevation view thereof;
FIG. 4 is a right side elevation view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a first perspective view thereof;
FIG. 8 is a second perspective view thereof; and,
FIG. 9 is an enlargement of a portion of FIG. 1 denoted by a broken-line circle therein.
The broken lines immediately adjacent the shaded areas represent the bounds of the claimed design while all other broken lines depict environment. The broken lines form no part of the claimed design.