[auth][mob] Fall back to Passcode if FaceId not detected on iOS (#6396)

## Description
Fallback to Pin/Passcode on iOS if fail to detect TouchID/FaceID

auth/lib/utils/auth_util.dart

@@ -53,6 +53,7 @@ Future<bool> requestAuthentication(
           signInTitle: l10n.androidSignInTitle,
         ),
         IOSAuthMessages(
+          localizedFallbackTitle: l10n.enterPassword,
           goToSettingsButton: l10n.goToSettings,
           goToSettingsDescription: l10n.goToSettings,
           lockOut: l10n.iOSLockOut,

mobile/lib/utils/auth_util.dart

@@ -46,6 +46,7 @@ Future<bool> requestAuthentication(
           signInTitle: S.of(context).androidSignInTitle,
         ),
         IOSAuthMessages(
+          localizedFallbackTitle: S.of(context).enterPassword,
           goToSettingsButton: S.of(context).goToSettings,
           goToSettingsDescription: S.of(context).goToSettings,
           lockOut: S.of(context).iOSLockOut,