The ornamental design for a spring clip, as shown and described.
FIG. 1 is a front elevation view of a spring clip in an open position, the rear elevation view being a mirror image thereof;
FIG. 2 is a top plan view thereof;
FIG. 3 is a right side elevation view of the spring clip of FIG. 1, the left side elevation view being a mirror image thereof;
FIG. 4 is a front elevation view of the spring clip of FIG. 1 in a compressed position for insertion and holding of an object, the left side elevation view being a mirror image thereof; and,
FIG. 5 is a right side elevation view of the spring clip of FIG. 1, the left side elevation view being a mirror image thereof.