The ornamental design for an in-ear headphone, as shown and described.
FIG. 1 is a front right perspective view of an ornamental design for an in-ear headphone, according to the invention.
FIG. 2 is a front view of the in-ear headphone of FIG. 1.
FIG. 3 is a back view of the in-ear headphone of FIG. 1.
FIG. 4 is a top view of the in-ear headphone of FIG. 1.
FIG. 5 is a bottom view of the in-ear headphone of FIG. 1.
FIG. 6 is a right view of the in-ear headphone of FIG. 1; and,
FIG. 7 is a left view of the in-ear headphone of FIG. 1.
The claimed design is shaded in FIGS. 1 through 7. The dashed lines in the figures are for environmental purposes only and form no part of the claimed design.