curl https://api.portkey.ai/v1/assistants/asst_abc123 \
  -H "Content-Type: application/json" \
  -H "x-portkey-api-key: $PORTKEY_API_KEY" \
  -H "x-portkey-virtual-key: $PORTKEY_PROVIDER_VIRTUAL_KEY" \
  -H "OpenAI-Beta: assistants=v2" \
  -X DELETE

{
  "id": "<string>",
  "deleted": true,
  "object": "assistant.deleted"
}