The ornamental design for a harness for pets, as shown and described.
1. Harness for pets
1.1: Perspective
1.2: Front
1.3: Back
1.4: Left
1.5: Right
1.6: Top
1.7: Bottom
1. This article according to the present design is made of synthetic fiber, synthetic resin, and metal; 2. This article according to the present design is worn on a pet, and includes rings to which a strap is connected; 3. Figure 1.1is a perspective view of the present design, Figure 1.2is a front view of the present design, Figure 1.3is a rear view of the present design, Figure 1.4is a left side view of the present design, Figure 1.5is a right side view of the present design, Figure 1.6is a top view of the present design, and Figure 1.7is a bottom view of the present design.