The ornamental design for a cap, as shown and described.
FIG. 1 is a front perspective view of the cap according to the present invention;
FIG. 2 is a rear elevational view of the cap of FIG. 1;
FIG. 3 is a front elevational view of the cap of FIG. 1;
FIG. 4 is a right side elevational view of the cap of FIG. 1;
FIG. 5 is a left side elevational view of the cap of FIG. 1.
FIG. 6 is a top plan view of the cap shown in FIG. 1; and,
FIG. 7 is a bottom plan view of the cap shown in FIG. 1, wherein the dot-dash broken line shown within the interior of the cap defines the bounds of the design and forms no part thereof.