The ornamental design for a watercloset, as shown and described.
FIG. 1 is a perspective view of front, top plan and right side of a water closet showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a left side view thereof; and,
FIG. 7 is a right side view thereof.
The broken lines shown in the drawings views are included for the purpose of illustrating a portion of the water closet that forms no part of the claimed design.