release: Update changelog for release v0.9.0

Author: cdecker

CHANGELOG.md

@@ -5,7 +5,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 
-## [0.9.0rc4] - 2020-07-28
+## [0.9.0] - 2020-07-31: "Rat Poison Squared on Steroids"
 
 ### Added
 
@@ -785,7 +785,7 @@ There predate the BOLT specifications, and are only of vague historic interest:
 6. [0.5.1] - 2016-10-21
 7. [0.5.2] - 2016-11-21: "Bitcoin Savings & Trust Daily Interest II"
 
-[0.9.0rc4]: https://github.com/ElementsProject/lightning/releases/tag/v0.9.0rc4
+[0.9.0]: https://github.com/ElementsProject/lightning/releases/tag/v0.9.0
 [0.8.2]: https://github.com/ElementsProject/lightning/releases/tag/v0.8.2
 [0.8.1]: https://github.com/ElementsProject/lightning/releases/tag/v0.8.1
 [0.8.0]: https://github.com/ElementsProject/lightning/releases/tag/v0.8.0