Fix wrong path in readme

Author: konstin

setup.py

@@ -11,9 +11,7 @@
     url="https://github.com/PyO3/setuptools-rust",
     keywords="distutils setuptools rust",
     description="Setuptools rust extension plugin",
-    long_description="\n\n".join(
-        (open("README.rst").read(), open("CHANGES.rst").read())
-    ),
+    long_description=open("README.rst").read(),
     license="MIT",
     packages=["setuptools_rust"],
     install_requires=["semantic_version>=2.6.0", "toml>=0.9.0"],