[firebase-release] Removed change log and reset repo after 13.3.1 release

Author: google-oss-bot

CHANGELOG.md

@@ -1,7 +0,0 @@
-- Release Cloud Firestore emulator v1.19.1:
-  - Adds support for Datastore Mode to the Firstore Emulator. Adds
-    `--database-mode` flag to `gcloud emulator firestore start` command. Note
-    that this is a preview feature and if you find any bugs, please file them
-    here: <https://github.com/firebase/firebase-tools/issues>.
-- Improve FAH onboarding flow to connect backends with SCMs (#6764).
-- Fixed issue where GitHub actions would fail due to lack of permission. (#6791)