We claim the ornamental design for a vacuum cleaner, as shown and described.
FIG. 1 is a front and right side perspective view of a vacuum cleaner showing our new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a right side elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a rear elevation view thereof;
FIG. 6 is a top plan view thereof; and,
FIG. 7 is a bottom plan view thereof.
The details shown in broken lines form no part of the claimed design. The upper solid lines in FIGS. 1-4 delimit the portion of the housing included in the design and are not contour lines.