message: doc(interface-types) Fix a typo.
diff: @@ -202,7 +202,7 @@ impl<'de, 'a> de::Deserializer<'de> for &'a mut Deserializer<'de> {
  Some(InterfaceValue::String(_)) => self.deserialize_string(visitor),
  Some(InterfaceValue::I32(_)) => self.deserialize_i32(visitor),
  Some(InterfaceValue::I64(_)) => self.deserialize_i64(visitor),
  - Some(InterfaceValue::Record(_)) => unreachable!("Records should have been flatten."), // already flatten
  + Some(InterfaceValue::Record(_)) => unreachable!("Records should have been flattened."), // already flattened
  None => Err(DeserializeError::InputEmpty),
  }
  }
  