The ornamental design for a grillinggrid, as shown and described.
FIG. 1 is a top perspective view of a grilling grid showing my new design;
FIG. 2 is a top plan view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a front elevational view thereof; the rear being a mirror image; and,
FIG. 5 is a left side elevational view thereof; the right side being a mirror image.
The broken lines in FIGS. 1 to 4 showing screws for fastening the handles of the grilling grid to the base of the grilling grid form no part of the claimed design.