The ornamental design for a pillow, as shown and described.
FIG. 1 is a perspective view of a pillow, showing my new design in use, with a parent and child shown in broken lines which form no part of the claimed design;
FIG. 2 is a perspective view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a front view thereof; and,
FIG. 6 is a bottom view thereof.
The left side view is a mirror image of the right side view and the rear view is a mirror image of the front view.