Cleanup legacy code

app/src/main/kotlin/com/hippo/ehviewer/Settings.kt

@@ -112,7 +112,6 @@ object Settings : DataStorePreferences(null) {
     val predictiveNavAnim = boolPref("predictive_nav_anim", true)
     val blackDarkTheme = boolPref("black_dark_theme", false)
 
-    val needSignInFlow: Flow<Boolean>
     var downloadScheme by stringOrNullPref("image_scheme", null)
     var downloadAuthority by stringOrNullPref("image_authority", null)
     var downloadPath by stringOrNullPref("image_path", null)
@@ -146,7 +145,7 @@ object Settings : DataStorePreferences(null) {
     var saveCrashLog by boolPref("save_crash_log", true)
     var security by boolPref("require_unlock", false)
     var removeImageFiles by boolPref("include_pic", true)
-    var needSignIn by boolPref("need_sign_in", true).also { needSignInFlow = it.valueFlow() }
+    var needSignIn by boolPref("need_sign_in", true)
     var harmonizeCategoryColor by boolPref("harmonize_category_color", true)
     var preloadThumbAggressively by boolPref("preload_thumb_aggressively", false)
     var downloadOriginImage by boolPref("download_origin_image", false)