[firebase-release] Removed change log and reset repo after 15.3.0 release

Author: google-oss-bot

CHANGELOG.md

@@ -1,6 +0,0 @@
-- Fixed pricing calculation for Cloud Functions deployed to newer regions (africa-south1, europe-west8, me-west1, and others) when using minInstances. (#9696)
-- Removed MCP tools and prompts that required Gemini in Firebase terms of service.
-- Fixes an issue where the `--only` flag was not always respected for `firebase mcp`
-- Removed timeout when connecting to Cloud SQL. Hopefully, should mitigate issue #9314. (#9725)
-- Added `/firestore:generate_rules` and `/storage:generate_rules` MCP prompts.
-- Update Data Connect Emulator to 3.0.2, which addresses some internal errors #9738