fix: flutter analyze

Author: LucasXu0

frontend/appflowy_flutter/lib/mobile/presentation/home/mobile_home_setting_page.dart

@@ -71,12 +71,6 @@ class _MobileHomeSettingPageState extends State<MobileHomeSettingPage> {
   }
 
   Widget _buildSettingsWidget(UserProfilePB userProfile) {
-    // show the third-party sign in buttons if user logged in with local session and auth is enabled.
-
-    final isLocalAuthEnabled =
-        userProfile.authenticator == AuthenticatorPB.Local && isAuthEnabled;
-    '';
-
     return BlocProvider(
       create: (context) => UserWorkspaceBloc(userProfile: userProfile)
         ..add(const UserWorkspaceEvent.initial()),

frontend/appflowy_flutter/lib/user/presentation/screens/sign_in_screen/mobile_sign_in_screen.dart

@@ -22,8 +22,6 @@ class MobileSignInScreen extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    const double spacing = 16;
-
     return BlocBuilder<SignInBloc, SignInState>(
       builder: (context, state) {
         final theme = AppFlowyTheme.of(context);