The ornamental design for a lawnsweeper, as shown and described.
FIG. 1 is a front, right, top side perspective view of a lawn sweeper showing my new design;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a left side elevational view thereof;
FIG. 6 is a top plan view thereof;
FIG. 7 is a bottom plan view thereof; and,
FIG. 8 is a rear, left, top side perspective view thereof.
The broken line showing of the wheels is included for the purpose of illustrating portions of the lawn sweeper and forms no part of the claimed design.