Clean up change log. (#6347)

Author: schnecle

FirebaseAppDistribution/CHANGELOG.md

@@ -1,6 +1,6 @@
 # Unreleased
 - [changed] Updated header comments (#6321).
-- [fixed] Bug for customers with restricted api keys unable to fetch releases.
+- [fixed] Bug for customers with restricted API keys unable to fetch releases (#6346).
 
 # v0.9.0
 - Initial beta release.