Update README.rst

Author: lewzylu

README.rst

@@ -1,7 +1,7 @@
 Qcloud COSv5 SDK
 #######################
 
-.. image:: https://img.shields.io/pypi/v/nine.svg
+.. image:: https://img.shields.io/pypi/v/cos-python-sdk-v5.svg
    :target: https://pypi.org/search/?q=cos-python-sdk-v5
    :alt: Pypi
 .. image:: https://travis-ci.org/tencentyun/cos-python-sdk-v5.svg?branch=master