The ornamental design for a watch, as shown and described.
FIG. 1 is a front elevation view of a watch that has the design.
FIG. 2 is a left side elevation view of the watch.
FIG. 3 is a right side elevation view of the watch.
FIG. 4 is a rear elevation view of the watch.
FIG. 5 is a top view of the watch.
FIG. 6 is a bottom view of the watch; and,
FIG. 7 is a right front perspective view of the watch.
The structural feature depicted by broken lines in FIG. 4 has been shown for the purpose of illustrating a portion of the watch that forms no part of the claimed design.