Fix return value in mesh edge contact in nativeccd.

PiperOrigin-RevId: 730924994
Change-Id: Iab4f26da126713bae6629eef502bb2aad690c595

Author: kbayes

src/engine/engine_collision_gjk.c

@@ -1828,7 +1828,7 @@ static int meshEdgeNormals(mjtNum* res, mjtNum* endverts, int dim, mjCCDObj* obj
         }
       }
     }
-    return 3;
+    return v1_num;
   }
   return 0;
 }