I claim the ornamental design for an insole, as shown and described.
FIG. 1 is a bottom perspective view of the claimed design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof
FIG. 4 is a top view thereof;
FIG. 5 is a bottom view thereof;
FIG. 6 is a left side view thereof; and,
FIG. 7 is a right side view thereof.
The ornamental design which is claimed is shown in solid lines in the drawings. The dash-dot boundary line defines the boundary of the claimed design and forms no part of the claimed design. The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design.