The ornamental design for a watch, as shown and described.
FIG. 1 is a right side view of the watch of my design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is a top perspective view thereof.
The structural features depicted by broken lines in FIG. 6 are shown for the purpose of illustrating portions of the watch that form no part of the claimed design.