Refactor: Replace REQWESTCONFIG with initialize_reqwest_client

so that we don't need two `OnceCell`s.

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

src/fetchers/quickinstall.rs

@@ -88,7 +88,7 @@ impl QuickInstall {
             let url = Url::parse(&stats_url)?;
             debug!("Sending installation report to quickinstall ({url})");
 
-            new_reqwest_client()?
+            new_reqwest_client()
                 .request(Method::HEAD, url.clone())
                 .send()
                 .await