fix iOS build issue

src/accounts.rs

@@ -314,7 +314,7 @@ impl Accounts {
     /// Performs a background fetch for all accounts in parallel with a timeout.
     ///
     /// If you want no timeout, then use [Accounts::background_fetch] instead.
-    pub async fn background_fetch_with_timeout(&self, timeout: Duration) -> Result<()> {
+    pub async fn background_fetch_with_timeout(&self, timeout: std::time::Duration) -> Result<()> {
         tokio::time::timeout(timeout, self.background_fetch()).await?;
         Ok(())
     }