The ornamental design for the toilet pan, as shown and described:
FIG. 1 is an isometric view of the toilet pan showing our new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a right-hand side elevational view thereof, the left-hand side being a mirror image thereof;
FIG. 5 is a bottom plan view thereof; and,
FIG. 6 is a rear elevational view thereof.
The broken lines in FIGS. 2, 5, and 6 are included for the purpose of illustrating internal portions of the toilet pan which form no part of the claimed design.