Update recaptchaVerifier docs (firebase#6460)

Author: sam-gc

packages/auth/src/platform_browser/recaptcha/recaptcha_verifier.ts

@@ -85,10 +85,6 @@ export class RecaptchaVerifier implements ApplicationVerifierInternal {
  * 'invisible'.
  *
  * @param authExtern - The corresponding Firebase {@link Auth} instance.
- *
- * @remarks
- * If none is provided, the default Firebase {@link Auth} instance is used. A Firebase {@link Auth} instance
- * must be initialized with an API key, otherwise an error will be thrown.
  */
  constructor(
  containerOrId: HTMLElement | string,