The ornamental design for a fence, as shown and described.
FIG. 1 is a front perspective view of the fence;
FIG. 2 is a top plan view of the fence of FIG. 1;
FIG. 3 is a front elevational view of the fence of FIG. 1;
FIG. 4 is a right side clevational view of the fence of FIG. 1;
FIG. 5 is a rear elevational view of the fence of FIG. 1;
FIG. 6 is a left side elevational view of the fence of FIG. 1; and,
FIG. 7 is a bottom plan view of the fence of FIG. 1.
The broken line showing the middle section of the fence in FIG. 1 is illustrative of environmental structure only and forms no part of the claimed design.