The ornamental design for a pettoilet, as shown and described.
FIG. 1 is a perspective view of a pet toilet, showing my new design;
FIG. 2 is a top view thereof:
FIG. 3 is a bottom view thereof;
FIG. 4 is a front view thereof,
FIG. 5 is a back view thereof; and,
FIG. 6 is a right side view thereof, the left side view being a mirror image of the right side.
The even dash-dash broken lines depict portions of the pet toilet that form no part of the claimed design. The dot-dash lines depict bounds of the claim and form no part of the claimed design.