The ornamental design for a chair, as shown and described.
FIG. 1 is a front perspective view of a chair;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left elevation view thereof, the right elevation view being a mirror image thereof; and,
FIG. 5 is a top plan view thereof.
The spaces between adjacent panels are defined by the uniformly flat peripheral surfaces of each panel, as can be partially seen in FIGS. 1 and 5. Thus, such uniformly flat peripheral surfaces have not curvatures or voids.
The broken lines shown in the drawings depict portions of the chair that form no part of the claimed design.