The ornamental design for a hairstraightener, as shown and described.
FIG. 1 is a top, front and right side perspective view of a hair straightener showing my new design;
FIG. 2 is a bottom, rear and left side perspective view thereof;
FIG. 3 is a front elevational view thereof;
FIG. 4 is a back elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a right side elevational view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof;
FIG. 9 is an enlarged view of the selected portion in FIG. 1; and,
FIG. 10 is an enlarged view of the selected portion in FIG. 1.
The broken lines shown in the drawings depict portions of the hair straightener in which the design is embodied that form no part of the claimed design.