I claim the ornamental design for an electronic device, as shown and described.
FIG. 1 is a front perspective view of an electronic device showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a front perspective view thereof shown in an example environment.
The broken lines depicting an upper element in FIG. 8 represent an environment, and all other broken lines represent portions of the electronic device that form no part of the claimed design.