The ornamental design for a watchdial, as shown and described.
FIG. 1 is a right-top perspective view of the watch dial;
FIG. 2 is a top view of the watch dial;
FIG. 3 is a front view of the watch dial;
FIG. 4 is a rear side view of the watch dial;
FIG. 5 is a right side view of the watch dial; and,
FIG. 6 is a left side view of the watch dial.
The broken lines in the drawings are used to show a watch case and hands that do not form part of the claimed design. The portions of the watch dial that are not disclosed are not part of the claimed design.