The ornamental design for a posture brace, as shown and described.
FIG. 1 is a front perspective view of a posture brace, showing my new design;
FIG. 2 is a front elevation view of FIG. 1, the rear elevation view being a mirror image thereof;
FIG. 3 is a left side elevation view of FIG. 1, the right side elevation view being a mirror image thereof; and,
FIG. 4 is a top plan view of FIG. 1, the bottom plan view being a mirror image thereof.
The broken lines shown in the drawings depict portions of the posture brace that form part of the claimed design.
The posture brace is shown with symbolic breaks in its length. The appearance of any portion of the article between the break lines forms not part of the claimed design.