Drop unused avatar pref

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

@@ -168,7 +168,6 @@ object Settings : DataStorePreferences(null) {
     var userAgent by stringPref("user_agent", CHROME_USER_AGENT)
     var defaultDownloadLabel by stringOrNullPref("default_download_label", null)
     var displayName by stringOrNullPref("display_name", null)
-    var avatar by stringOrNullPref("avatar", null)
     var language by stringPref("app_language", "system").observed { updateWhenLocaleChanges() }
     var lastUpdateTime by longPref("last_update_time", 0)
     var favDialogTheta by floatPref("fav_select_dialog_delta", 0F)

app/src/main/kotlin/com/hippo/ehviewer/client/EhUtils.kt

@@ -153,7 +153,6 @@ object EhUtils {
 
     fun signOut() {
         EhCookieStore.signOut()
-        Settings.avatar = null
         Settings.displayName = null
         Settings.gallerySite = EhUrl.SITE_E
         Settings.needSignIn = true

app/src/main/kotlin/com/hippo/ehviewer/ui/login/PostLogin.kt

@@ -13,7 +13,6 @@ suspend fun postLogin() = coroutineScope {
         runCatching {
             EhEngine.getProfile().run {
                 Settings.displayName = displayName
-                Settings.avatar = avatar
             }
         }.onFailure {
             logcat(it)