The ornamental design for an autoinjector, as shown and described.
FIG. 1 is a front bottom perspective view of an autoinjector showing our new design;
FIG. 2 is a front top perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a left side view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a top view thereof.
The broken lines immediately adjacent to the shaded areas represent the bounds of the claimed design and form no part thereof. The broken lines showing the remainder of the autoinjector form no part of the claimed design.