The ornamental design for a chair, as shown and described.
FIG. 1 is a perspective view of a chair.
FIG. 2 is a front view of the chair of FIG. 1.
FIG. 3 is a rear view of the chair of FIG. 1.
FIG. 4 is a side view of the chair of FIG. 1.
FIG. 5 is a side view of the chair of FIG. 1.
FIG. 6 is a top view of the chair of FIG. 1; and,
FIG. 7 is a bottom view of the chair of FIG. 1.
The dash dot dash broken lines illustrate boundaries of the claimed design. The dash dash dash broken lines illustrate unclaimed portions of the chair.