The ornamental design for a watch, as shown and described.
1.1is a front view of a watch showing the new design;
1.2is a right side view thereof;
1.3is a left side view thereof;
1.4is a rear view thereof;
1.5is a bottom view thereof;
1.6is a top view thereof; and
1.7is a front, bottom, right side perspective view thereof.
The broken line showing of strap attachment features in figures 1.5, 1.6, and 1.7is for the purpose of illustrating environmental structure and forms no part of the claimed design.