The ornamental design for a cuplid, as shown and described.
FIG. 1 is a perspective view of a cup lid, showing my new design;
FIG. 2 is a first side view thereof;
FIG. 3 is a second side view thereof;
FIG. 4 is a third side view thereof;
FIG. 5 is a fourth side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is an exploded perspective view thereof.
The broken lines and the areas within and adjacent to the shaded surfaces in FIGS. 3 and 7 depict portions of the cup lid that form no part of the claimed design.