The ornamental design for a dog harness, as shown and described.
FIG. 1 is a top front left isometric view of a design of a dog harness, showing our new design.
FIG. 2 is a top rear left isometric view thereof.
FIG. 3 is a bottom rear left isometric view thereof.
FIG. 4 is a bottom front left isometric view thereof.
FIG. 5 is a rear view thereof.
FIG. 6 is a front view thereof.
FIG. 7 is a left-side view thereof.
FIG. 8 is a right-side view thereof.
FIG. 9 is a top view thereof.
FIG. 10 is a bottom view thereof.
FIG. 11 is a front perspective view, shown within an environment of use; and,
FIG. 12 is a rear perspective view thereof.
The broken lines depict portions of the article that form no part of the claimed design. In FIG. 11 and FIG. 12, the broken lines depicting a dog represent environmental subject matter that forms no part of the claimed design.