The ornamental design for a sidewall marking of a vehicle tire, as shown and described.
FIG. 1 is a front view of a vehicle tire, showing my new design;
FIG. 2 is a perspective view showing the sidewall marking on a sidewall of the vehicle tire; and,
FIG. 3 is a side view thereof.
In the drawings, the broken lines defining the outline of the tire and the inner bead depict environmental subject matter that forms no part of the claimed design.