The ornamental design for a stereoconnector, as shown and described.
FIG. 1 is a perspective view of the stereo connector;
FIG. 2 is a front view of the stereo connector;
FIG. 3 is a rear view of the stereo connector;
FIG. 4 is a first side view of the stereo connector;
FIG. 5 is a second side view of the stereo connector;
FIG. 6 is a top view of the stereo connector; and,
FIG. 7 is a bottom view of the stereo connector.
The broken lines showing in the figures are included for the purpose of illustrating portions of the stereo connector that form no part of the claimed design.