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