The ornamental design for a fireplace, as shown and described.
FIG. 1 is a front perspective view of fireplace showing my new and original design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a top view thereof;
FIG. 4 is a right side elevation view thereof; and,
FIG. 5 is a left side elevation view thereof.
The broken lines in the drawing represent unclaimed portions of the fireplace. The rear, bottom and top of the design form no part of the claimed design.