The ornamental design for a shirt, as shown and described.
FIG. 1 is a front perspective view of a shirt showing my new design in an in-use configuration;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a side view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a rear perspective view thereof.
The broken lines immediately adjacent to the shaded area represent unclaimed boundaries of the design. The unshaded regions, demarcated by broken lines, represent unclaimed portions of the shirt and form no part of the claimed design. The broken lines showing the remainder of the shirt form no part of the claimed design. The contrast shading represents a contrast in appearance only and does not represent any particular color, material, texture or finish.