The ornamental design for a chair, as shown and described.
FIG. 1 is a front perspective view of a chair showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left-side elevation view thereof;
FIG. 5 is a right-side elevation view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The dash-dash broken lines shown on the top and bottom surfaces of the chair cushion represent stitching and form part of the claimed design. The additional dash-dash broken lines shown on the bottom surface of the article in FIG. 7 illustrate portions of the article that form no part of the claimed design.