The ornamental design for a cap, as shown and described.
FIG. 1 is a perspective view of a cap;
FIG. 2 is a left elevation view of the design illustrated in FIG. 1;
FIG. 3 is a top elevation view of the design illustrated in FIG. 1;
FIG. 4 is a right elevation view of the design illustrated in FIG. 1;
FIG. 5 is a bottom plan view of the design illustrated in FIG. 1;
FIG. 6 is a front elevation view of the design illustrated in FIG. 1; and,
FIG. 7 is a rear elevation view of the design illustrated in FIG. 1.
The crosshatched pattern, although shown intermittently, is understood to be distributed uniformly over the surfaces of the claimed design and represents fabric.