The ornamental design for a hairdryer, as shown and described.
FIG. 1 is a perspective view of a hair dryer showing my new design;
FIG. 2 is a front view of FIG.1;
FIG. 3 is a rear view of FIG. 1;
FIG. 4 is a right side view of FIG. 1;
FIG. 5 is a left side view of FIG. 1;
FIG. 6 is a top plan view of FIG. 1; and,
FIG. 7 is a bottom view of FIG. 1.
The dashed broken lines in the drawings are for the purpose of illustrating portions of the hair dryer that form no part of the claimed design. The dot-dashed broken lines define the bounds of the claimed design and form no part thereof.