I claim the ornamental design for a pin cap, as shown and described.
FIG. 1 is a perspective view of a pin cap showing my new design; shown fixed to a receiver pin assembly,
FIG. 2 is a perspective view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a side elevation view thereof;
FIG. 5 is a front elevation view thereof; and,
FIG. 6 is a bottom plan view thereof.
The broken line showing of a receiver pin assembly is for environmental purposes only and forms no part of the claimed design. The broken line showing of the upper and lower portions of a pin cap defines the boundary of the claimed design.