[firebase-release] Removed change log and reset repo after 15.21.0 release

Author: google-oss-bot

CHANGELOG.md

@@ -1,11 +0,0 @@
-- Fixed an issue where `login:*`, `target:*`, and `ext:*` subcommands were missing from `firebase --help`.
-- Functions can declare additional API dependencies (#10621)
-- Added mock Passkey (WebAuthn) support to the Auth emulator. (#10636)
-- Fixes `spawn activate.bat ENOENT` error on Windows when initializing Python functions. (#10608)
-- Fixed an issue where Cloud Run rewrites in the Hosting emulator would always hit the live Cloud Run API instead of routing to the local functions emulator. (#10588)
-- Removed temporary warning directing Dart functions users to Cloud Console, as Firebase Console now supports Dart functions. (#10584)
-- Updated the Firebase Data Connect local toolkit to v3.4.11, which includes the following changes:
-  - [changed] Updated the Golang dependency version to 1.25.11.
-- Fixed issue where `apptesting:execute` command rejects documented `--test-username`, `--test-password`, and `--test-password-file` options.
-- Updated Web Frameworks to warn about missing SSRF protection config in Angular 22 deploys (#10523)
-- Fixed an issue where Astro 6 SSR deploys returned HTTP 500 by preserving the `server/` directory in the generated Cloud Function. (#10537)