Note auth error callbacks are deprecated

Author: hsubox76

packages/auth/src/model/public_types.ts

@@ -242,11 +242,12 @@ export interface Auth {
   /**
    * Adds an observer for changes to the user's sign-in state.
    *
-   * @remarks
    * To keep the old behavior, see {@link Auth.onIdTokenChanged}.
    *
    * @param nextOrObserver - callback triggered on change.
-   * @param error - callback triggered on error.
+   * @param error - Deprecated. This callback is never triggered. Errors
+   * on signing in/out can be caught in promises returned from
+   * sign-in/sign-out functions.
    * @param completed - callback triggered when observer is removed.
    */
   onAuthStateChanged(
@@ -274,7 +275,9 @@ export interface Auth {
    * This includes sign-in, sign-out, and token refresh events.
    *
    * @param nextOrObserver - callback triggered on change.
-   * @param error - callback triggered on error.
+   * @param error - Deprecated. This callback is never triggered. Errors
+   * on signing in/out can be caught in promises returned from
+   * sign-in/sign-out functions.
    * @param completed - callback triggered when observer is removed.
    */
   onIdTokenChanged(