We claim the ornamental design for the insole, as shown and described.
FIG. 1 is a top view of a left foot insole according to the present design;
FIG. 2 is a left side view of the insole of FIG. 1;
FIG. 3 is a bottom view of the insole of FIG. 1;
FIG. 4 is a back end view of the insole of FIG. 1; and,
FIG. 5 is a top perspective view of the insole of FIG. 1.
The oval hole through the insole and the dots surrounding and leading away from the oval hole are claimed aspects of the design. The dashed broken lines shown are included for the purpose of illustrating portions of the insole that form no part of the claim.