Prepare 1.9.0 release

Signed-off-by: Kai Hudalla <[email protected]>

Author: sophokles73

Diff for: site/homepage/content/release-notes.md

@@ -4,7 +4,7 @@ title = "What is new & noteworthy in Hono?"
 description = "Information about changes in recent Hono releases. Includes new features, fixes, enhancements and API changes."
 +++
 
-## 1.9.0 (not yet released)
+## 1.9.0
 
 ### New Features