We claim the ornamental design for a computing device, as shown and described.
FIG. 1 is a front perspective view of a computing device;
FIG. 2 is a front view thereof;
FIG. 3 is a right side view thereof, the left side being a mirror image of the right side; and,
FIG. 4 is a top view thereof.
The broken lines in the drawings are shown for environment only and form no part of the claimed design. The short-dash, long-dash lines are boundary lines and form no part of the claimed design.