The ornamental design for support harness, as shown and described.
FIG. 1 is a front perspective view of a support harness for securing a person to an anchor point, showing my new, original and ornamental design, all broken or dash line features shown in FIGS. 1-8 are for illustrative purposes and are not part of the claimed design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view;
FIG. 4 is right side view;
FIG. 5 is a left side view;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view; and,
FIG. 8 is a perspective view of the support harness in use, the person is shown in broken lines for illustration purposes and is not part of the claimed design.