The ornamental design for a side table, as shown and described.
FIG. 1 is a top right side perspective view of the side table showing our new design;
FIG. 2 is a bottom right side perspective view of the side table showing our new design;
FIG. 3 is a rear view of the side table showing our new design;
FIG. 4 is a front view of the side table showing our new design;
FIG. 5 is a right side view of the side table, with a left side view being omitted since it is a mirror image of the right side view from side-to-side;
FIG. 6 is a top view of the side table showing our new design; and,
FIG. 7 is a bottom view of the side table showing our new design.