update readme

Author: 32ethers

docs/source/market_deribit_option.md

@@ -12,7 +12,7 @@ Therefore, we set up a service to record orderbooks via [Deribit api](https://do
 
 To save resources, we collect data once per hour. The data collection is limited to ETH.
 
-The collected data has been uploaded to [Dropbox](https://www.dropbox.com/scl/fo/kwk5kgiseu5rvccjscd0f/ANswtRLzpCxOc6cMTH0oRlE?rlkey=ai071f9695uz287lt8k0bci5e&e=1&st=ntbog1sr&dl=0). If you need to conduct options backtesting, you'll need to download historical order books first.
+The collected data has been uploaded to https://www.dropbox.com/scl/fo/kwk5kgiseu5rvccjscd0f/ANswtRLzpCxOc6cMTH0oRlE?rlkey=ai071f9695uz287lt8k0bci5e&e=1&st=ntbog1sr&dl=0. If you need to conduct options backtesting, you'll need to download historical order books first.
 
 During backtesting, you can select the desired orders from the current order book and then purchase them directly or buy them at specific prices. Transaction fees for buying and selling options will also be calculated.