Arden Cho says she experienced a racist attack in which a man threatened to kill her. The “Teen Wolf” star was walking her dog Wednesday night when the man screamed “I’m going to motherf—g kill you c— and your f—g dog,” she said in an emotional Instagram post. Cho, 35, said the man shouted other obscenities at her from just a couple feet away. She picked up her dog and ran home. “I’m not crying anymore but I’m still scared, I’m still shaking,” Cho wrote. “I used to run at night, I haven’t run in months. I still have to walk my dog, so I carry a knife when we go out at night. I know how to figh…