We claim the ornamental design for a cutting insert, as shown and described.
FIG. 1 is an isometric view from above of a cutting insert showing my new design;
FIG. 2 is a top plan view of the cutting insert of FIG. 1;
FIG. 3 is a bottom plan view of the cutting insert of FIG. 1;
FIG. 4 is a front view of the cutting insert of FIG. 1;
FIG. 5 is a rear view of the cutting insert of FIG. 1;
FIG. 6 is a right side view of the cutting insert of FIG. 1; and,
FIG. 7 is a left side view of the cutting insert of FIG. 1.
The broken line showings of FIGS. 1-7 are included for the purposes of illustrating portions of the cutting insert and form no part of the claimed design.