Upgrade to Firebase auth 8.2.9 (#1881)
Upgrade to Firebase auth 8.2.9 (#1881)

Changes to auth since 8.2.1:

- API update for an internal package. There is no change in the public API.
- Fixed a bug where UTF-8 encoded strings were not decoded in getIdTokenResult. See https://github.com/firebase/firebase-js-sdk/issues/4174.
- Added the useEmulator() function and emulatorConfig to the firebase package externs.
google/exposure-notifications-verification-server,google/exposure-notifications-verification-server,google/exposure-notifications-verification-server,google/exposure-notifications-verification-server