Remove RefCell around autenticator - they are sync now

src/rust/api/client.rs

@@ -613,7 +613,7 @@ pub struct ResumableUploadHelper<'a, A: 'a> {
     >,
     pub delegate: &'a mut dyn Delegate,
     pub start_at: Option<u64>,
-    pub auth: &'a mut A,
+    pub auth: &'a A,
     pub user_agent: &'a str,
     pub auth_header: String,
     pub url: &'a str,