The ornamental design for a garmenthangerhook, as shown and described.
FIG. 1 is a top perspective view of a garment hanger hook showing my design;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a back view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a top view thereof; and,
FIG. 8 is a bottom view thereof.
The broken lines showing the hanger body in FIGS. 1 through 8 are for purposes of showing environmental structure only and they form no part of the claimed design.