DOC: update dependency on finance-python

Dockerfile

@@ -16,7 +16,7 @@ WORKDIR /
 COPY ./requirements.txt /requirements.txt
 RUN pip install numpy==1.19.1 -i https://pypi.douban.com/simple
 RUN pip install -r /requirements.txt -i https://pypi.douban.com/simple
-RUN pip install finance-python==0.8.1 -i https://pypi.douban.com/simple
+RUN pip install finance-python>=0.8.1 -i https://pypi.douban.com/simple
 
 COPY ./setup.py /setup.py
 COPY ./setup.cfg /setup.cfg