message: refactor error msg for RequestError
diff: @@ -135,22 +135,19 @@ pub enum RequestError {
  #[error("invalid update: the model or scalar sent by the participant could not be aggregated")]
  AggregationFailed,
  - #[error("invalid update: the seed dictionary sent by the participant is invalid")]
  - InvalidLocalSeedDict,
  -
  #[error("the request could not be processed due to an internal error")]
  InternalError,
  - #[error("Redis failed: {0}")]
  + #[error("redis failed: {0}")]
  Redis(#[from] RedisError),
  - #[error("{0}")]
  + #[error(transparent)]
  SeedDictUpdate(#[from] SeedDictUpdateError),
  - #[error("{0}")]
  + #[error(transparent)]
  SumDictAdd(#[from] SumDictAddError),
  - #[error("{0}")]
  + #[error(transparent)]
  MaskDictIncr(#[from] MaskDictIncrError),
  }
  