The ornamental design for a shirt, as shown and described.
FIG. 1 is a front elevational view of a shirt in a state of use in which it is supported in the shape of a human male torso;
FIG. 2 is a rear elevational view of the shirt in the state of use in which it is supported in the shape of a human male torso;
FIG. 3 is a right side elevational view of the shirt in the state of use in which it is supported in the shape of a human male torso; and,
FIG. 4 is a left side elevational view of the shirt in the state of use in which it is supported in the shape of a human male torso.
The dash-dot-dash broken lines and unshaded areas within illustrate portions of the Shirt that form no part of the claimed design. The dashed lines showing buttons form no part of the claimed design. The short dash-dash broken lines represent stitching.