Hair Straightener

FIG. 1 is a top, front, right side perspective view of a hair straightener, showing my new design; FIG. 2 is a bottom, rear, left side perspective view thereof; FIG. 3 is a front view thereof; FIG. 4 is a back view thereof; FIG. 5 is a left view thereof; FIG. 6 is a right view thereof; FIG. 7 is a top view thereof; FIG. 8 is a bottom view thereof; and, FIG. 9 is a front, right, top side perspective view thereof, in another configuration. The broken lines in the drawings depict portions of the hair straightener that form no part of the claimed design.