The ornamental design for a mirror, as shown and described.
FIG. 1 is a front perspective view of the design showing the right-hand
side of the design, the left-hand side is a mirror image of the right-hand
side,
FIG. 2 is a front view of FIG. 1,
FIG. 3 is a top view of FIG. 1; and,
FIG. 4 is a right-hand side view of FIG. 1 and the left-hand side view is a
mirror image.
The rear of the mirror is not part of the claimed design.