The ornamental design for a gateway, as shown and described.
FIG. 1 is a perspective view of a gateway showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a side view thereof;
FIG. 5 is another side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The broken lines that are immediately adjacent to the claim, and define unshaded regions, represent the bounds of the claim, while all other broken lines are directed to environment; the broken lines form no part of the claimed design. In addition, the unshaded surface in the FIG. 3 view that directly adjoins the claimed solid line edge forms no part of the claimed design.