We claim the ornamental design for a forage harvester, as shown and described.
FIG. 1 is a rear perspective view of a forage harvester showing our new design;
FIG. 2 is a side view thereof;
FIG. 3 is an opposing side view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a front view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is a rear perspective view of a forage harvester showing a second embodiment of our new design;
FIG. 9 is a side view thereof;
FIG. 10 is an opposing side view thereof;
FIG. 11 is a rear view thereof;
FIG. 12 is a front view thereof;
FIG. 13 is a top view thereof; and,
FIG. 14 is a bottom view thereof.
Only the shapes and portions bounded by solid lines form the claimed design. The elements depicted in dashed lines are shown for illustrative purpose of environment and form no part of the ornamental design.