The ornamental design for a pottyseat, as shown and described.
FIG. 1 is a front, left, and bottom perspective view of a potty seat, showing my design.
FIG. 2 is a rear and right perspective view thereof.
FIG. 3 is a front elevation view thereof.
FIG. 4 is a rear elevation view thereof.
FIG. 5 is a left side elevation thereof.
FIG. 6 is a right side elevation thereof.
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken lines shown in the drawings are included for the purpose of illustrating portions of the potty seat that form no part of the claimed design.