The ornamental design for a chair, as shown and described.
FIG. 1 is a perspective view of the chair showing my 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 an opposite side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The chair has a rattan or faux rattan surface thereon. The features presented in broken lines are for environmental purposes only and form no part of the claimed design.