I claim the ornamental design for a watch band, as shown and described.
FIG. 1 is a front view of the watch band;
FIG. 2 is a back view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a perspective view thereof.
The bolder dashed lines shown in the drawings illustrate part of the claimed design, and the light dashed lines in the drawings illustrate portions of the watchband and form no part of the claimed design.