The ornamental design for a maraca, as shown and described.
FIG. 1 is a top perspective view of a maraca;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a front elevational view thereof, with the rear elevation being a mirror image thereof;
FIG. 4 is a top plan view thereof; and,
FIG. 5 is a bottom plan view thereof.
The broken line showing of the handle and dotted pattern on the maraca surface in FIGS. 1-5 are included for the purpose of showing environmental structure and form no part of the claimed design.