message: [json-rpc] Remove unneeded mut for JsonRpcClient
  Closes:
  Approved by: thefallentree
diff: @@ -27,7 +27,7 @@ impl JsonRpcClient {
  /// Sends a JSON RPC batched request.
  /// Returns a vector of responses s.t. response order matches the request order
  - pub fn execute(&mut self, batch: JsonRpcBatch) -> Result<Vec<Result<JsonRpcResponse>>> {
  + pub fn execute(&self, batch: JsonRpcBatch) -> Result<Vec<Result<JsonRpcResponse>>> {
  if batch.requests.is_empty() {
  return Ok(vec![]);
  }
  @@ -49,7 +49,7 @@ impl JsonRpcClient {
  // send with retry
  pub fn send_with_retry(
  - &mut self,
  + &self,
  request: serde_json::Value,
  ) -> Result<reqwest::blocking::Response> {
  let mut response = self.send(&request);
  @@ -63,7 +63,7 @@ impl JsonRpcClient {
  response
  }
  - fn send(&mut self, request: &serde_json::Value) -> Result<reqwest::blocking::Response> {
  + fn send(&self, request: &serde_json::Value) -> Result<reqwest::blocking::Response> {
  self.client
  .post(self.url.clone())
  .json(request)
  