The ornamental design for a necktie, as shown and described.
FIG. 1 is a top front perspective view of a necktie;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a right elevation view thereof;
FIG. 5 is a left elevation view thereof;
FIG. 6 is a top elevation view thereof;
FIG. 7 is a bottom elevation view thereof; and,
FIG. 8 is a top front perspective view thereof, shown in use.
The partial human figure outlined by broken lines in FIG. 8 assists to illustrate how the necktie may appear when worn and forms no part of the claimed design.