We claim the ornamental design for a refrigerator, as shown and described.
FIG. 1 is a front perspective view of a refrigerator showing our new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is another front perspective view thereof.
The broken lines in the drawings depict portions of the refrigerator that form no part of the claimed design. The dot-dash broken lines represent a boundary of the claimed design and form no part thereof.