[firebase-release] Removed change log and reset repo after 6.7.0 release

changelog.txt

@@ -1,8 +0,0 @@
-feature - Adds ability to deploy scheduled functions
-fixed - Fixes a bug in Cloud Firestore emulator where rulesets with no-op writes would modify a document's updated_at timestamp.
-fixed - Reduces lock contention in Cloud Firestore emulator during concurrent writes to a document.
-feature - Serving Hosting locally can now proxy to the live Cloud Run service.
-fixed - Fixes a bug where fields in Cloud Firestore indexes would be sorted alphabetically for display.
-fixed - Fixes a bug in Firestore Emulator REST API that caused 404s to root collections.
-fixed - Firestore Emulator now accepts secure JWTs from Android/iOS SDK with warnings.
-fixed - Lifecycle hooks will respect a single multi-resource deploy.