fix suplicate battery encoding on website

rust/src/webserver/webserver.rs

@@ -228,8 +228,7 @@ fn get_battery_state(
 ) -> Result<Option<std::string::String>, anyhow::Error> {
     let mut board = BOARD_ACCESS.lock().expect("board access");
     let battery_state = board.board_hal.get_battery_monitor().get_battery_state();
-    let battery_json = serde_json::to_string(&battery_state)?;
-    anyhow::Ok(Some(battery_json))
+    anyhow::Ok(Some(battery_state))
 }
 
 fn get_log(