The ornamental design for a potholder, as shown and described.
FIG. 1 is a perspective front view of a pot holder;
FIG. 2 is a front elevation view of the pot holder;
FIG. 3 is a rear elevation view of the pot holder;
FIG. 4 is a left elevation view of the pot holder;
FIG. 5 is a right elevation view of the pot holder;
FIG. 6 is a top elevation view of the pot holder;
FIG. 7 is a bottom elevation view of the pot holder; and,
FIG. 8 is a perspective view of the pot holder in an alternate position, as worn by a person.
The broken lines shown in FIG. 8 representing a hand and arm are included for the purpose of illustrating environmental structure and form no part of the claimed design.