The ornamental design for a watchdial, as shown and described.
FIG. 1 is a front elevational view of a watch dial showing our new design;
FIG. 2 is a back elevational view thereof;
FIG. 3 is a right side elevational view thereof;
FIG. 4 is a left side elevational view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a front, right side perspective view thereof.
The broken lines in the drawing figures depict unclaimed subject matter that form no part of the claimed design, and the broken lines in FIGS. 1 and 7 represent the boundary of the claimed design.