The ornamental design for a gateway, as shown and described.
FIG. 1 is a front perspective view of a gateway showing our new design;
FIG. 2 is a top view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a right side view thereof; and,
FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 2.
The uneven-length broken lines immediately adjacent to and surrounding the shaded area define the boundary of the claimed design and form no part thereof. The even-length broken lines depicting the remainder of the gateway form no part of the claimed design.