The ornamental design for a support brace, as shown and described.
FIG. 1 is a front perspective view of a support brace showing the claimed design;
FIG. 2 is a front view thereof;
FIG. 3 is a back view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof; and,
FIG. 7 is a bottom view thereof.
The dashed broken lines in the figures show portions of the support brace that form no part of the claimed design. The dot-dash broken lines in the figures show boundaries that form no part of the claimed design. The shade lines in the figures show contour and not surface ornamentation.