Fix README

Author: okue

README.rst

@@ -1002,8 +1002,8 @@ And more... TBD
    :target: https://travis-ci.org/line/line-bot-sdk-python
 .. |PyPI version| image:: https://badge.fury.io/py/line-bot-sdk.svg
    :target: https://badge.fury.io/py/line-bot-sdk
-.. |Documentation Status| image:: https://readthedocs.org/projects/line-bot-sdk-python/badge/?version=latest
-   :target: http://line-bot-sdk-python.readthedocs.io/en/latest/?badge=latest
+.. |Documentation Status| image:: https://readthedocs.org/projects/line-bot-sdk-python/badge/?version=stable
+   :target: http://line-bot-sdk-python.readthedocs.io/en/stable
 
 License
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