The ornamental design for a fireplace, as shown and described.
FIG. 1 is a perspective view of a fireplace;
FIG. 2 is another perspective view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a top side view thereof, the bottom side being a mirror image; and,
FIG. 6 is a right side view thereof, the left side being a mirror image.
The broken line showing of parts of the drawings is included for the purpose of illustrating use and environment and forms no part of the claimed design.