FIG. 1 is a top, right-side, and front view of a vacuum cleaner, showing the new design. FIG. 2 is a front view of the vacuum cleaner. FIG. 3 is a right-side view of the vacuum cleaner. FIG. 4 is a left-side view of the vacuum cleaner. FIG. 5 is a back view of the vacuum cleaner; and, FIG. 6 is a top view of the vacuum cleaner. The broken lines represent portions of the vacuum cleaner that form no part of the claimed design.