The ornamental design for the gopher stick, as shown.
FIG. 1 is a perspective view depicting an embodiment of the gopher stick as disclosed herein (the gopher and ground pictured is for illustrative purposes only and forms no part of the claimed invention);
FIG. 2 is an enlarged side view depicting an embodiment of the gopher stick as disclosed herein; and,
FIG. 3 is a top view depicting an embodiment of the gopher stick as disclosed herein.