don't set json content-type/accept headers for download requests

the response type is NOT json, this was just wrong

src/main.rs

@@ -548,8 +548,9 @@ async fn download_versions(
             debug!(?url, "downloading...");
             let req = http_client
                 .get(url)
-                .header(CONTENT_TYPE, "application/json")
+                //.header(CONTENT_TYPE, "application/json")
-                .header(ACCEPT, "application/json");
+                //.header(ACCEPT, "application/json")
+                ;
 
             let req = if let Some(token) = config.registry.auth_token.as_deref() {
                 req.header(AUTHORIZATION, token)