[Fix]Update data preparation part in README.md (#1924)

Author: YeewahChan

README.md

@@ -200,7 +200,7 @@ Here is an example to download the latest data.
 ```bash
 wget https://github.com/chenditc/investment_data/releases/latest/download/qlib_bin.tar.gz
 mkdir -p ~/.qlib/qlib_data/cn_data
-tar -zxvf qlib_bin.tar.gz -C ~/.qlib/qlib_data/cn_data --strip-components=2
+tar -zxvf qlib_bin.tar.gz -C ~/.qlib/qlib_data/cn_data --strip-components=1
 rm -f qlib_bin.tar.gz
 ```