Update README.md

Link to stable docs

README.md

@@ -1,6 +1,6 @@
 [![Actions Status](https://github.com/bytewax/bytewax-interval/workflows/CI/badge.svg)](https://github.com/bytewax/bytewax-interval/actions)
 [![PyPI](https://img.shields.io/pypi/v/bytewax-interval.svg?style=flat-square)](https://pypi.org/project/bytewax-interval/)
-[![Bytewax User Guide](https://img.shields.io/badge/user-guide-brightgreen?style=flat-square)](https://docs.bytewax.io/projects/bytewax-interval/en/latest/index.html)
+[![Bytewax User Guide](https://img.shields.io/badge/user-guide-brightgreen?style=flat-square)](https://docs.bytewax.io/projects/bytewax-interval/en/stable/index.html)
 
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