Update CHANGELOG.md

Author: Akuli

CHANGELOG.md

@@ -2,7 +2,7 @@ Unlike the Git commit history, this changelog does not include code cleanups
 and other details that don't affect using Porcupine.
 
 
-## v2022.08.28
+## Unreleased
 
 Yesterday's release (below) turned out to be broken: syntax highlighting didn't work at all. This release fixes that.