I claim the ornamental design for a pet harness, as shown and described.
FIG. 1 is a perspective view of a pet harness, showing my new design in a fitted configuration;
FIG. 2 is a perspective view of FIG. 1, illustrated in a flat configuration;
FIG. 3 is a left-side elevational view of FIG. 2, the right-side elevational view being a mirror image thereof;
FIG. 4 is a front elevational view of FIG. 2, the rear elevational view being a mirror image thereof;
FIG. 5 is a top plan view of FIG. 2; and,
FIG. 6 is a bottom plan view of FIG. 2.
The broken lines showing a pet in FIG. 1 and an oval central portion on the sling in the figures depict environmental matter and form no part of the claimed design. The remaining broken lines represent stitching, and are part of the claimed design.