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 broken lines shown in FIGS. 1-7 of the drawings illustrate stitching that form part of the claimed design. The additional broken lines in FIG. 7 depict environmental subject matter and form no part of the claimed design.