The ornamental design for a watercloset, as shown and described.
FIG. 1 is a perspective view 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 left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines in the figures are included for the purpose of illustrating the unclaimed portions of the water closet and form no part of the claimed design. The dot-dash lines define the bounds of the claimed design and form no part thereof.