The ornamental design for ravioli, as shown and described.
FIG. 1 is a front view of the ravioli;
FIG. 2 is a rear view of the ravioli;
FIG. 3 is a left side view of the ravioli, the right side view being identical thereto;
FIG. 4 is a top view of the ravioli; and,
FIG. 5 is a bottom view of the ravioli.
The small-dash broken lines in FIGS. 1-5 illustrate portions of the ravioli that form no part of the claimed design. The large-dash broken lines in FIGS. 1-5 illustrate the boundary of the claimed design and form no part thereof.