The ornamental design for a watch, as shown and described.
FIG. 1 is a right front perspective view of a watch showing my new design; and,
FIG. 2 is a front elevational view thereof.
The structural features depicted by broken lines have been shown for the purpose of illustrating portions of the watch that form no part of the claimed design.
The sides and rear of the watch, not shown, form no part of the claimed design.