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