The ornamental design for a snowbreaker, as shown.
FIG. 1 is a perspective view of a snow breaker showing my new design:
FIG. 2 is a perspective view thereof of the top, back and left side;
FIG. 3 is a top plan view thereof; and,
FIG. 4 is a bottom plan view thereof.
The broken lines shown in the drawings are for the purpose of illustrating unclaimed portions of the snow breaker and form no part of the claimed design.